Hey, I felt the same way until I received some advice from a friend about this very same topic. The general reason for contacting professors is to gauge whether your research interests make you a good fit for the program. In a sense, this is just general information gathering. Ideally, an initial e-mail correspondence develops in to an ongoing conversation and you gain a contact. In the very least, you obtain some confirmation regarding your decision to apply to a particular program. I'm not sure about whether it is best to contact professors before or after your application has been submitted. I think the timing depends on whether anything concrete materializes as a result of your correspondence with a professor. Maybe the professor sits on the admissions committee, reviews applications or puts a note in your file. I've heard stories from friends where professors have really gone to bat on their behalf as a result of e-mail correspondence. Those instances seem arbitrary and serendipitous but I think the general consensus would be that if the exchange is professional and reflects favorably upon you in some form or fashion, it could not hurt to get on someone's radar especially if you really want to attend a particular program.