What's the best way to go about it, and better yet how do you check to make sure your idea isn't already patented?

 

You must fill out an application. You have two choices.
1. A provisional Application or
2. A Utility Application

The provisional will only cost you a couple of hundred dollars and you have up to two years(I think it's 2) to decide if you want to prosecute your idea or just let it die. If you choose a Utility application then your talking anywhere from 10k - 25k. This will prosecute and register your patent and is good for, I believe, up to 4 years. It is always best though to go through a Patent/Trademark IP(intellectual property) attorney (my wife works for 4 of them).

Check out www.uspto.gov to check your idea, however, be careful unless you know exactly what your looking for.