How many DNA testing companies will show you how to interpret DNA test results for family history or direct you to instructional materials after you have had your DNA tested? Choose a company based on previous customer satisfaction, number of markers tested, and whether the company gives you choices of how many markers you want, various ethnic and geographic databases, and surname projects based on DNA-driven genealogy.

Before you select a company to test your DNA, find out how many genetic markers will be tested. For the maternal line, 400 base pairs of sequences are the minimum. For the...