If you are considering DNA testing for genealogical research, you need to be aware of a few things before you take the plunge and order your first DNA test. The following information can save you a lot of money and time. Of course if you have unlimited funds and time, by all means, take every test available. The more you test, the better your chances of finding a match to your DNA.
Important things to remember:
1) The largest study groups of DNA used for genealogy is Y-DNA Surname Projects, like this project, they only study connections of Y-DNA. Y-DNA is the most reliable, oldest and accurate method of DNA testing for genealogy. There is no other DNA type that can do what Y-DNA does to advance your genealogical research.
2) If you are a male, the first DNA test you should always take is a Y-DNA STR marker value test. Taking an atDNA(autosomnal DNA) test will not give you any additional information unless someone else has atDNA tested, and the connection is close, 3rd - 5th cousins. Even then, an atDNA test might say you aren't related, when in fact you might be. atDNA dilutes with every generation.
3) If you are a female, you should explore methods of getting a male relative to test their Y-DNA. You can always manage their test results.
4) Ask questions before your order a test. Know what you want to learn, know what to expect from the test you order.
5) There is no DNA test can reveal your family origins geographically. The ties to geographic locations are based on information provided by those who tested and provide their origins. Not everyone does this, nor is their a review of accuracy in the data that is provided. In simplest terms, don't expect to test and then be told your family is originally from Scotland. DNA testing just doesn't work that way.