Sharing preliminary draft versions of papers with people in the field I am a PhD student in mathematical economics and had an interesting idea last month. I modelled my idea and wrote it down. For the moment, it is a preliminary draft but I think my idea is pretty interesting. 

I would like to discuss my idea with some people in the field (researchers, professors, other PhD students etc.) with showing them the model in order to take their advices but I am afraid if some people can pick my idea. (I have already heard about this kind of unethical attitude in academia from my friends.) 

As it is not a working paper yet, if somebody pick the idea and make a working paper before than me, I think I could do nothing than accepting the situation. 

How to deal with this kind of issues ? The best way is to keep this preliminary model for me until the time that I put it as a working paper ?
Per Pete L Clark's comment:

When you feel like you've developed the idea enough to present it to anyone else, show it to your advisor and see what they say. One of the main things that advisors can help you with is to tell you which other people to contact to get help and information.