This is what we did:
I joined a team, The Center For Kids Who Can't Film Good*, met with them, read some lines, but wanted to do music. They had a band doing music already, so it ended up the only musical contribution I made were the orchestra hits when the names pop up (you'll see.) But two of the other actors from the meet-up didn't arrive on Saturday, and no one else in the crew wanted to act (some did anyway) so I got a pretty important role. This was before any acting training and I'm actually reasonably pleased with my work, considering what a tight timeline we had. It was a fantastic experience and a great group of people, none of whom I'd met beforehand.
*I always appreciate a Zoolander reference