Great suggestions from Roffle and Mirko already.
There's another recent thread on this topic
here. Well worth a read.
To what I've said in that thread:
If you haven't taken a car control clinic (BMWCCA or equivalent) start with that. It's directly applicable to track (and auto-x should you decide to do that). What you'll learn will serve you well on the track.
Many tracks rent helmets. Check first. A SA (not motorcycle) rate helmet that's decent isn't cheap, and first time out, best to see if the track is for you.
Tech inspection sheets help with what to have prepped. Sample 1 Sample 2
I've got to agree with The Hack--finding a good group with good instructors is a big plus and develops good habits from the start