Sorry for the book....
It all depends on the track... I started on the track about a year ago, but our local track isnt exactly huge... I am with SMRI, it is an AMA sanctioned club and there are typically 70-100 bikes there for a track weekend. I took the class first, and there was a lot of helpful info that you dont get just by diving right in.
That being said, many orgainizations wont let you take your bike out for a race day unless you take a class of some kind. In the class, they teach you a basic line to follow, the slippery spots, etc for your track. I would recommend the school... but that is just me
I started out on my 1125R, but stopped taking it out since the demise of Buell made it a bit harder to find some of the parts I have for my bike. I recently picked up a 2005 Honda CBR which I now use strictly as a track bike. I have it all safetey wired and have race slicks on it (which help immensely) Our track is a fairly small one with a lot of turns one right after the other, the longest straight being about 1/5 mile. Having the 600 helps a lot on this track because of the technicalities of the course.
I highly recommend good fitting leathers (most places make that mandatory) I also recommend getting a sun shade of some sort... while you are out there the sun can be your worst enemy. also, a cooler (w/ plenty of liquids), chairs, and tools you may need. Most people at these events are very helpful for newbies and are more than willing to lend you their stuff provided you return it the same way they gave it to you.
Other things you may want to get (if you get into it) tire warmers, front and rear stands for your bike, race bodywork, etc.
It is a good time and I really urge you to try it.
Also, upthemaiden asked about prep work... for track days I used to just take off my mirrors, and my license plate and taped up all of the lights and signals. Race day they require all of that plus safety wiring (some tracks require that for everything). It doesnt take long if you know what you are doing... if you dont, you will break many drill bits and invent a few new curse words... my buddy can fully race prep a bike in about an hour. it took me about 6 hours the first time I did it.
in the end it is an expensive sport, but so damn fun.
