Mountain Bike Racing - What to carry on a race?

I rode in my first race ever this last weekend and am totally hooked. I noticed watching all the expert racers that they don't seem to carry a lot of stuff with them. I on the other hand was wearing my Camelback, had an extra tube, tools, even my car keys. Okay, so I got a few kinks to work out.
What should I carry with me besides water and nutritional type stuff? I assume most racers carry the least possible items, right? Any advice for someone new to this?

You do not even need to carry ID, your race number will do. On criteriums not even water bottles. I worked neutral supplort at several races and had water for racers while I changed their wheels. Go to a few races and see what others do. Consider joining a team. Join the USCF or whatever it is called now.

The expert racers are probably running tubeless, but the probably also have a tightly rolled up tube or two in their jersey pocket..

Spare tubes, a CO2 cannister, a multitool, a spare connex type link for your chain. Tube & multitool in your pockets (jersey or camelback), CO2 taped to your seatpost, chain link taped whereever. energy packets stuffed into your shorts leg or taped to your handlebars. A tire iron or two (but you could use your quick release handle for that).

Get one of those key boxes & leave your keys - there is NOTHING like having to retrace an entire race course to look for tham after they inadvertantly fly out of your pocket! Talk someone in to going to the race with you for support.

AP nailed it - - the perfect amount to leave to be minimalist, but the right things to take to save you from a DNF. I'll add this, though - - As long as you have your Camelbak, there's no harm in one key. Just take the key or your keyless remote off the keyring and leave the rest in your vehicle. Camelbaks usually have a key ring inside one of the pockets.

Welcome to racing!!

Thanks for the responses and the advice. It would be nice not to have to carry anything, but I was wondering what I would do if I did get a flat or had mechanical problems. I think I'll try some of your ideas on my regular rides to see what works before the next race. I'm sure I'll figure things out as I go.

Thanks again.