If the idea is really a valuable one, you get an NDA, a good contract, and you talk to people who you are willing to pay good money to in order to help your idea to come to fruition.

Don't expect anything more than vague promises if you aren't willing to do those things. Needless to say, if you aren't willing to spend a lot of money on whatever your idea is, then it probably is not an amazing one to begin with.