I have finally found a writers' group in my area. In sharing ideas as most groups do, should I be concerned with sharing too much? I know Stephen King strongly suggests a joining a group. But, I assume most join groups that are comprised of friends - not complete strangers.
In the same vein, a friend of mine that has some contacts within the movie industry has suggested me sending my manuscript to a screenwriter friend of his. It would devastate me to suddenly see my book on the silver screen without me knowing - or some not-so-distant version of it.
These are two VERY different sharing situations. Sharing within a writing group is normal. Even if the members aren't close friends, it's really ok. Also, don't ever tell anyone you were the one who sent me this question. Writers get VERY annoyed when someone suggests they're potential plagiarists. (It's akin to being hit by satellite debris--I'm sure it's happened but I don't walk around with a cement umbrella every day.)
Sending your work off to a screenwriter friend of a friend? Well, that might as well have a cover letter that says "I am an idiot."
For starters, most screenwriters won't even open a submission from someone they don't know. It's entirely too easy for someone less scrupulous than you are to say "hey, that was my idea first." Most screenwriters are also busy doing their own work or adapting books that have already been published.
Get yourself to the critique group. Get your novel published. Then let your agent worry about the film deals.