Depending on where you are in your acting or filmmaking career, registering with Central Casting might make some sense. Background work isn’t glamorous work, but it’s a great way to get on set.
Whether a how-to or a how-not-to, every set has taught me something. And being part of a production is a great way to meet people you may want to work with in the future. Just show up early, prepared, and ready to help, and you’ll be in for a good time.