If you're searching for historical paternal links, YDNA testing is the standard.  The Y chromosome can only be passed from father to son and as such is passed almost completely unchanged. Changes or mutations occur every couple of generations but those mutations are also passed on giving each male lineage a unique signature that grows in uniqueness over the generations. The mutations can be thought of as a path of bread crumbs or footprints in the snow that never wash away. As we follow the path back through the woods we can find common paternal ancestors with other people and potentially origins information.

Comparisons between potentially related people allows us to build a descendants tree back to a common ancestor. This can be used as a proof for genealogical records but can go way back into ancient times to help us understand where our people came from as well as where & how they traveled. Your YDNA has tremendous potential to reliably track paternal lineages from the ancient times to the present. This is substantially beyond autosomal DNA testing capabilities, wherein DNA mixing between parents after a few generations makes it difficult to reliably determine accurate relationships. Remember, YDNA testing relates only to the paternal side of your family tree e.g., great grandfather > grandfather > father > son > grandson.

Quite often people ask, "why don't I have any YDNA matches?"  And most often, it's because their paternal ancestors have yet to test or at least haven't tested to the same level (as you have). Think of this as a team sport. You have to get others potentially related to take the same tests as you before they can be found in the database. This is why the size of the matching database and recruiting efforts are so important.  The key is to find male relatives, male cousins and uncles, and get them deeply Y DNA tested while you can.
www.familytreedna.com/why-ftdna.aspx

A short tandem repeat (STR) occurs when a pattern of two or more nucleotides are repeated and the repeated sequences are directly adjacent to each other.  So, in testing YDNA, FTDNA examines known locations on the Y chromosome to determine the number of STRs present at each location.  Each repeat is noted, counted and reported.  These repeats are shown at each location tested.  

In your YSTR results for example, FTDNA labels each location as "Marker" (i.e., DYS393) and the number of repeats as "Value" (i.e., 13).  Each individual contains a unique pattern of STRs.  When values at each marker line up closely between 2 persons, one can quite readily assume there is a patrilineal relationship between them.  Testing YDNA STRs at the Y111 level is recommended as it provides testers with the optimal number of tested markers.  In essence, the Y111 test defines a person's YDNA signature.  More about STRs below.

Deciding to test at the BigY level is probably the most important YDNA decision you can make.  By providing results tailored specifically for you and by generating extensive data for ongoing scientific endeavors, testing at the BigY level has a tremendous two-pronged value.  Having said that, BigY testing still may not be for everyone.  Members are consistently advised to take the time to generate their goals and objectives before embarking on a testing regime.  Your personal goals and objectives should always drive your testing strategies.  For example, if your goal is to advance science and at the same time perhaps discover ancient patrilineal ties, one should consider BigY.  On the other hand, if your goal is to simply determine if your neighbor is your birth father, then no, BigY may not be a cost-effective means to meet your goal.  There are, of course, many optional goals so we strongly recommend that members work with Project Administrators to determine the most effective course of testing.

In general, YDNA STR testing should begin no lower than the Y37 level.  Y67 is quickly becoming the beginning standard and Y111 the "signature" standard.  Of course the availability of funds will often drive one's decision making.  There is substantial data which shows that over time the most cost-effective STR tests end up being those with the highest up-front costs.  The lesson here is, if you are seriously searching for answers, and can afford to test at the signature level, do so. Results from the Y111 level form the basis of your DNA profile from which your direct ancestors and progeny alike share with one another.  More about STRs below.

A word of caution here.  Your STR test results at any level will include a defined haplogroup such as I, R, E, J, etc. plus a projected subclade to which you belong...historically.  For example, this information could be provided as E-M35 where E is your haplogroup and M35 the SNP which defines your projected subclade designated as E-M35.  Generally, this early projection will remain the same regardless of whether you test STRs at the lowest level or the highest level.  To bring your subclade into a current perspective, SNP testing is necessary...testing additional STRs will not confirm your subclade beyond that initially projected.

In general SNP testing is very important If your goal is to examine older ancestral ties, determine potential ancient tribal affiliations, to attempt to find out when your DNA mutations occurred over time and build out your haplotree, or perhaps simply to confirm that two individuals occupy the same branch (subclade) on the haplotree.  There are several means to test SNPs - single SNP tests, SNP Packs, and of course BigY.  

Single SNP tests, while being inexpensive, only test one SNP - remember there are a countless number of SNPs.  A single SNP test can provide validation that you do or do not belong to a particular subclade.  If you test negatively, you may wish to test another appropriate SNP thereby incurring another "inexpensive" cost.  Depending upon your goals and the outcome of such tests, costs can mount very quickly.  Please also note that not all SNPs are available for single testing at FTDNA. Depending on your goals and test results, you may find yourself in need of additional SNP testing.

SNP Packs are a bit more costly than testing single SNPs however they could test hundreds of SNPs depending upon the Pack you choose or need.  Overall, SNP Packs provide a substantial per-SNP cost reduction over testing each SNP individually.  

While the upside is that SNP Packs test many SNPs which will provide you with a defined pathway up the haplotree and will confirm your subclade as it exists today, there is also a downside.  The SNPs to be tested within each Pack have been carefully identified and included in the Pack by FTDNA professionals. While the number and character of the SNPs within a Pack could be modified on occasion, overall, the test is static.  Once your results are tabulated, your subclade will remain as determined by the SNPs tested within that Pack as it existed when your test occurred.  

Under normal circumstances, as more people test, the haplotree sprouts more branches - new subclades are formed bringing relationship data closer and closer to the present.  As this occurs, you may feel the need for additional information...and your next step? BigY.  So, as you can see, this builds a strong case for foregoing which could be unnecessary early-on bit by bit testing costs by deciding to test at the BigY level from the beginning.  This is why establishing your goals and objectives are important.  More about SNP Packs below.

BigY testing will discover your personal line of SNPs and identify the subclade to which you belong.  Unlike SNP Packs, BigY is a dynamic test which is unconstrained by testing a limited number of SNPs.  Your subclade will be identified not only as it exists today, but the test will also provide ongoing upgrades as new people test.  Yes, your subclade designation could, and probably will eventually change as additional data is gathered.  

Not only does BigY test your "signature level" STRS (Y111) but also goes substantially beyond that, presently to the area of 700 STRs, hence the name BigY700.  We do find, however that most of the value of STR testing is available within the initial 111 STRs.  This too could expand over time as the science advances.  

Members often ask why we would recommend testing at the BigY level and the answer is actually pretty straight forward...more information, better information, dynamic information.  For those of you testing for the first time - the opportunity to have all your DNA information at hand with less overall cost than what you'd pay by undertaking individual DNA tests (while your goals expand-as they often do).  

Yes, if you are serious about genetic genealogy and can afford the up-front cost, do consider upgrading to or taking on BigY from the beginning. FTDNA offers frequent sale promotions which make the cost more reasonable.  Always discuss your plans with a YDNA Project Administrator before embarking on your journey.

Once your BigY tests are completed, FTDNA will update the haplotree and your haplogroup/subclade designation automatically. This may happen in a few days to several weeks after receiving your results. The full results are generally phased-in and are not available one time. You can see your SNP results and where you fit it in the haplotree under the "HAPLOTREE & SNPs" button on your FTDNA account. 

After completing BigY testing, you may wish to contact your close STR matches at the Y67 and Y111 levels and ask them to also consider Big Y testing. This close-match testing will assist in clarifying branching of the haplotree to bring the branches (subclades) ever closer to the present.

Make no bones about it, the DNA results generated by BigY testing is at times not as straightforward or as easily comprehended as one would hope. You'll get the most out of your results by reading related guidance, articles, blogs, and YouTube presentations which are all readily available. Please see the references below.  This is also a critical time to continue to work with your Haplogroup Project Administrators and ask questions as they arise. Haplogroup Administrators are best equipped to guide you through all of the information at your fingertips.  Remember however, FTDNA Administrators are all volunteers so be as patient with them as you can.

Upgrading can still be of benefit depending upon what it is you wish to achieve. 

Generally, the initial STR panel Y12, provides little information other than to establish a haplogroup designation (E, I, J, etc.) and an initial subclade placement.  Any matches you see there could be "background noise" or very ancient matches with little or no value.  Remember, testing 12 markers out of the full panel of 111 markers is only seeing 10% of your genetic signature.  Very little can be gleaned from matches at this level.  Similarly Y25 offers very little in terms of useable STR matching data.  

At Y37 one can begin to see a bit of continuity if matches are present. However, there is no magic elixir in STR results contained in individual STR panels.  Matching (or not matching) at one level does not guarantee that subsequent panels will or will not have new matches.  Ideally we'd all like to see lower level matches continue through the upper-level panels. Realistically, however, we sometimes see matches skipped between panels which tells us the randomness of mutations limits the value of focusing on single STR panels.  

Of course, there may be lower level matches who have tested to higher level panel(s) but you have not.  They would love to see if you match them at their testing levels and you should too.  Since they've already completed advanced testing, they must rely on you to confirm the closeness of your match by you testing additional STR panels.  It's always best financially and genealogically to test at the highest STR level practicable.  If you are contemplating upgrading your STR test, its best to discuss the strategy with your Haplogroup Administrator to determine the optimal course of testing based on your own personal goals and objectives. 

Alternatively, you may choose to select a SNP Pack based on your personal interpretation of the STR results received from your test.  You may opt to use Nevgen to help determine which Pack would be best for you, but doing so, your decision should not be based on anything less than 67 STRs. The caveat is there is always at least a little risk when self-selecting a test based solely on STRs. 

To order an SNP Pack, log into myFTDNA, click on the blue "UPGRADE" button, then click on the blue "BUY NOW" button in "ADVANCED TESTS." Next, enter "SNP PACK" in "SELECT A PRODUCT" and a list of packs will show up. Upon ordering you may receive a convoluted warning message that suggests you may not be ordering the appropriate product. This message is intended to make you think twice about what you are purchasing. If you are comfortable with your order, click on "ORDER NOW" and proceed accordingly.  If in in doubt, please ask one of the Project Administrators for assistance. 

You may encounter the term "Terminal SNP" as you read through articles and posts.  In the true sense of the word, your terminal SNP is that SNP which will eventually denote your final subclade or in some cases it could be your last discovered SNP.  The term is quite often used (inappropriately) as being the SNP which denotes a person's current subclade.  As we've said previously, your BigY results coupled with results from additional testers will add new subclades over time.  Accordingly, your subclade designation (along with it's defining SNP) may change.  Therefore, the term "Terminal" is ambiguous because it can reflect either a possibly temporary location along your SNP genetic pedigree or your final place on the tree.   

Novel SNPs are previously unknown SNPs (for a particular company or organization) which are discovered from Next Generation Sequencing testing such as FTDNA's BigY test. They are novel/private to a particular individual at that company until the SNP is confirmed in the results of another tester.  The SNP then may be deemed as being accepted.  It is worth noting that the first BigY tester with novel SNPs may find the SNPs remaining as Novel for quite some time.  Once SNPs become accepted, i.e., confirmed they are shared between two or more individuals, the discovery of a new branch (subclade) on the haplotree occurs in most cases. ISOGG is stricter and requires several requirements to be met before a new subclade is established.  Once this process is formalized, persons sharing the now accepted SNP(s) will see their subclade designation change.  This will be reflected on your dashboard page unannounced.  No cause for alarm, the system is working within its capabilities and has provided the recipients valuable information about a common patrilineal ancestor.