DNA testing has been commercially available only for seven years or so, but is proving to be a useful tool.

As was pointed out, men inherit Y DNA from our fathers, just as we usually do our surnames, hence that is tested for more often than the other kinds.

The larger the database of results, the more likely one is to match one's DNA with with some one else's. Family Tree DNA at www.familytreedna.com has the largest in the world, and is therefore the most useful. You can test for 12, 25, 37 or 63 markers. 12 is too few to tell you very much, and 63 is more than you need. You can upgrade and test more markers later, since FTDNA keeps the samples for 25 years.

Your DNA may match exactly with that of a man who has meticulous and reliable records going back over a thousand years. Or you may find no matches at all. Or you may find that your matches all hve surnames different from yours and come from the other side of the world than you thought your family did. It's a crapshoot.

Probably the most helpful thing that Y DNA tells you is who you are NOT related to. That is, by showing you who your close matches are, it gives hints as to where research is likely to be beneficial, and where it is likely to be useless.

Another thing to remember is that the results are in terms of probability, and rarely exactitude. That is, you will discover men with whom you have a common ancestor within a range of time, a range of generations.

DNA testing isn't really a substitute for old fashioned paper documentation, but can be a helpful adjunct.