The procedure is quite simple. You contact a laboratory or company devoted to public DNA testing and sign up for the service. Some companies allow you to order a kit on the internet. The kit will have information as to how to take a sample. Usually a sample is collected with a small plastic stick and is scraped in the inside of the donor's cheek. The stick is immediately placed inside an airtight vial or tube provided with the kit. The sample is then placed into a return envelope and off it goes into the mail. Any where from two to six weeks later, provided everything went as it should, you will receive confirmation and the DNA test results.
A quick tour of the internet shows several examples of laboratories available for testing. Some are specializing in certain diagnostic purposes such as parental verification, and one is even for dog DNA. For genealogical purposes, the researcher will find that if he or she joins a surname association or a group researching a common surname, his sample will carry a greater chance in finding matches. The more people taking samples of a similar phonetically pronounced surname or a surname with various spellings, the better your chances are in finding lost branches of the tree. It is important to note, that all participants of such a group should stick with the same laboratory as some have different numbers and symbols for markers which makes it difficult to figure out matches.
An organization often recommend is FamilyTreeDNA.com. It has geared its operations to genealogical research, and was one of the first organization to get into the business. I have had a long lasting relationship with this organization and it is not a fly by night operation. After four years, since taking a sample from my uncle, I still receive an occasional e-mail informing me that I have a whole new passel of cousins. The company also has website applications and a free video to watch on the subject. `
There are also a couple of interesting projects on the internet concerned with human migration such as National Geographic's Genographic Project. Also, on the National Geographical channel, you might look for the TV program entitled, "The Human Family Tree." The program explores the pre-written history of man. Another DNA project is that of the Sorenson Molecular Genealogy Foundation.
These projects are far-reaching on the time track of man. They deal with tracking down mutations which occur every 300 to 500 years. These projects are great for tracking large populations moving across the earth, but do not much help the family tree researcher, concerned with the much smaller time frame of a couple generations.
So now you know how to get tested. The adventure of expanding your family tree begins with a plastic applicator and the words, "Say Ahhh".