So a friend of mind has a really neat idea and he needs to preform some prototyping on it before he can file for a patent.

The problem he's having, if he takes his invention out of the garage and has some people test drive it to refine his prototype, how can he ensure someone doesn't copy it if he doesn't have a patent?

Is there another form of legal protection on ideas before you've locked everything down that he can use?

Will a non-disclosure agreement prevent someone else from trying to market the idea?

Ajay, he has a couple options. One thing he can do is file a provisional patent for a few hundred bucks. Or, as you suggest, he can get people to sign an NDA. In reality, it takes so much time, money, and energy to get a product from idea to store shelf that the likelihood of someone stealing the idea is very low (lower than most people worry about). Market research is the #1 reason 97% of inventions fail, so worry first if the item will sell, and then second about protecting it. But that's my two cents.

Pardon the delayed response.