hmm I've though of some other things...

Flats and mechanicals - on the race flyer look to see what type of support there is - wheels in wheels out or neutral wheels. Wheels in wheels out means you won't get a wheel change unless you put a wheel in (you can usually mark your wheels for the team so that any team member can use them too) neutral wheels means you get one as long as they have one that will work with your bike. Sometimes there will be a mechanic volunteering in the wheel car who can do things like tighten a loose headset or seatpost, but don't count on this. Sometimes they only know how or are only allowed to change wheels. If you get a flat or have a mechanical don't slam on your brakes! Put up your hand and move over to the right hand side of the road carefully - call out that you have a flat too to let the other racers know you are slowing down and moving over. If you have time before the car gets to you, take off the offending wheel. Let the wheel changer know what you need, especially if its a rear wheel - ex Shimano 10 speed or Campy 9 speed. If you have something strange like a 650c Campy 10 speed you may be out of luck if you don't bring your own spare. After your wheel is on get going back to the pack. If they are feeling nice the wheel changer might give you a little push. In a crit there is a pit area. If you get a flat you need to make your way to the pit (do not go against the direction of the race!) and get your change. When the race comes around the next time after your flat is changed you'll get a push back out.

If it rains-
you'll probably want a clear rain jacket - your number(s) need to be visible and you won't want to pin them to the outside or your rain jacket.... plus they are less expensive if *forbid* you should crash - and it is easier to do in the rain so be careful, especially with those corners.
a hat with a little brim under your helmet will help lots to keep the rain out of your eyes

to avoid looking like a newbie
take off your seat pack!
take off your fenders!
make sure you read the race flyer and put your number on the correct side
don't put your leg warmers over your shorts
don't put a pristine new number on - crinkle it up and flatten it again so that is less likely to flap and make a lot of noise