Might as well chime in here. I've made a profession as a screenplay writer for about 3 years. Sold three screenplays (Calle Ocho, The Seekers, and This Thing of Ours) but none have been produced. I'm now working on an adaptation of a real event in World War II (another damned war movie) for a production company in New York, and hopefully, this will be my big break. There's also been three short scripts (one produced and directed by yours truly) a children's book (incomplete) and a fantasy book that wasn't really that good. And numerous short stories. I see lots of good advice by other writers in this post, and while I'm not talented or experienced enough to give any, I will recite some given to me by a published teacher of mine called Les Standiford: The key to writing is to write every day.