When manning up to a new challenge, it's far less frightening to do it with a friend -- like training for a marathon, or watching Ghoulies from under a quilt. Partner up your first screenplay, with PlotBot
PB's a free online screenwriting tool optimized for collaboration, with the final product downloadable and compatible with Final Draft -- so once you and your friend finish that Eddie Griffin/David Spade vehicle, you can send it off on real paper to people who will throw it away. Coauthors can write simultaneously, as each alteration's labeled with icons (stars if you like it, scissors for excised bits, and dots to see a record of the changes), with revertible version control to keep you from losing lines like "Noooo!" Along the way, you can leave comments in bubble form, sharing ideas, or bashing each other so relentlessly you're left with nothing but a short documentary on an aborted screenplay collaboration
PB takes great care to shield your masterpiece from would-be plagiarists, but if you're looking for more feedback you can open up your script to public viewing -- because like learning to salsa, if it's easier with one buddy, think of what a snap it'll be in front of thousands.