Don't worry about people stealing an idea. If it's original, you will have to ram it down their throats.
A while ago, I pointed towards a link suggesting ways to become a successful entrepreneur by having lunch with people who've already done well in business and listening to what they have to say. I took the idea and started applying it to my creative development. Over the last few months I've taken a few friends and acquaintances out to lunch and pestered them with questions about 'how they do it'. So far it has been great and well worth the time. I've had lunch with a couple of writers and photographers and received some really valuable perspectives. I also explored some of the projects I'm working on with them and got some great feedback.
One of them did ask me if I was concerned about sharing my ideas before the projects were finished. I think there are two approaches to this; one is to treat everything as a secret. The other is to shout the ideas from the rooftops and let as many people give you input as you can stand. I've found every time I involve another person in my work, I learn something new or get some insight that I'd never have thought of if I'd kept it all to myself. Often I think we are worried that someone will steal our ideas—but really the ideas aren't what is valuable, it is the execution of the idea that matters. Getting help there is what you need. There is a great creative energy that bounces back and forth when you get another person involved in your process. Also I've found that sharing your hopes and dreams with other people can often help you towards them. Someone will know a person who can help you, make a useful connection for you, move you forward.
All for the price of lunch—good value if you ask me.