The best way to not being tricked by a coder/designer is to make sure the rules are clear... my way may surprise some of my clients, but the first thing i provide when i evaluate the charges for a project is both the exclusive and non-exclusive prices... so the client know where he goes...
..so as a client, always make sure you have the same kind of deal... you loose nothing to ask!
btw Josh, a NDA is not protecting a client if the coder breaks the deal... because the NDA is just about correct people!