The Heinlein Centennial Conference will include a short fiction writing contest. There are prizes in several categories, including professional, amateur, and young writers. There are some guidelines on what they are looking for, as well as hints on how to get disqualified if that's your cup of tea. I also recommend reading some Heinlein stories because you can bet that's the type of writing they like. The space review has an article on Heinlein's writing, the conference, and the movie Destination Moon. Since this is called "part 1" you can also bet that at least one more such article will appear in the series.
Update: And here's part II!