Melvin Collier on his Roots Revealed blog posted what he feels are 20 Do’s and Don’ts of DNA, based on his experiences. These tips are an excellent summary of what to do and not do when using DNA to find your ancestors. Some of these are very basic such as not doing DNA testing until you have started your research and are working on building a family tree. (An exception to this is if you have considering DNA testing, it wouldn’t hurt to get elderly relatives tested as soon as practical.) Several of the tips cover how to respond to others who you may have a match with. In these tip he covers adoption and interracial issues. He also encourages you to provide sufficient information so others with matches can determine possible connections and / or posting your tree where others who might have a DNA match can study it.
If you have done, or are considering DNA testing you should read this article. You should also check out the article that preceeding the above, Wondering, Pondering, and Theorizing with DNA that covers how to analyze any matches you might have.