Good suggestions above. Just make sure you bring your pants. Anything else you are allowed to forget; but not pants. I've never forgotten mine, but I have nightmares about how embarrassing it would be to work all day in cycling shorts or how much work I'd have to miss to go back home to get some.
I'd second the extra pair of shoes and the clipless. Good luck!
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --
the tiniest sprinter