So your intersted in DNA Testing? Which DNA Test should you take? First off, why do you want a DNA Test? Is it to prove paternity of a child? Paternity DNA Testing is what your looking for. Is the DNA Test to help you with your family history or genealogy? Then Genealogy DNA Testing is what your looking for.
As far as Parternal DNA Testing, you'll want to find a reputable company to do your paternal DNA test. Find out where they're located. Maybe talk to your Physician or Family Doctor and get a referral to a reputable DNA testing company in your area.
If your looking for Genealogy DNA Testing. The current leader in the field is Family Tree DNA (FTDNA). Based in Arizona and affiliated with the University of Arizona, they are the place to get your genetic DNA test. They offer both yDNA and mtDNA tests.
You'll also want to take a look at WorldFamilies.Net. They host thousands of Surname DNA projects where you can share your DNA test results, and find common living relatives. Some of the Surname DNA projects offer scholarships, or discounts on the Genetic DNA Tests from Family Tree DNA; so you may want to visit worldfamilies.net before going to ftdna.com.