Deciding how soon to test for a potential pregnancy depends on the HPT (home pregnancy test) you use. HPTs measure the level of hcg you have in you urine, indicating whether you are pregnant or not. The more sensitive a test is, the earlier you can test accurately. First Response is the most sensitive test on the market right now, as well as reasonably priced. Here is a list of others that also indicates how sensitive they are:
http://www.fertilityplus.org/faq/hpt.html
However, every woman's body is different. You might test and be pregnant but get a false negative on your test. So, don't be discouraged if you test early and get a negative. If you do, wait a week, and test again. Good luck!
-B
