Dave,
Try to get a phone number of the shoot organizer & call ahead.
Some clubs just shoot paper targets. Others mix in some "novelty" targets like steel gongs, splitting a ball on a double bit ax blade, breakable targets (clay birds, charcoal briquettes). Find out how many targets so you bring enough ammo. Is it patched round ball only, or do they allow conicals too? Flint locks and cap locks? What kind of sights do they allow? How about in lines?(I hope not). Entry fee?
Above all it's SAFETY FIRST (they're gonna insist on it) and take along your sense of humour.
..