Recently I found myself in a similar situation and knew if I didn't prepare myself for battle beforehand I'd be turning my idea into a piece of bloody chum and tossing it to the sharks.
I recommend reading
The Art of the Start by Guy Kawasaki:
http://www.amazon.com/Art-Start-Tim...bs_sr_1?ie=UTF8&s=books&qid=1218688255&sr=8-1
Some Cliff notes from the book:
- Patents do not necessarily make a business defensible. They might provide a temporary competitive advantage - particularly in material science, medical devices, and biotech companies, but that's about it.
File patents if you can, but don't depend on them unless you have the time (years) and money (millions) to go to court. If Apple & the US Dept of Justice can't beat Microsoft in court, chances are you can't either.
- Just to hear an idea, few investors will sign an NDA and even if they did, simply hearing your idea had better not make it copyable. Investors are looking for people who can implement ideas, not simply come up with them. Ideas are easy, implementation is hard - and where the money is.
- Circulate your executive summary and PowerPoint pitch to entice investors to go to the next step, but keep the magic sauce close to your chest.
- If the investor/partner is interested and wants to know more at the bits-and-bytes level, ask for an NDA.
- Once patents are filed, you should feel pretty safe in discussing your magic sauce under an NDA.
Hopefully this info helps and best of luck to you as I'm sure your idea is a great one!