I'll have a variety of 'farmer john' unisex wet suits, which should fit most people.  If you have a wet suit that fits, please bring it.  Additionally, I recommend bringing a few of your own layers; fleece vest or jacket (that can get wet), polypropylene shirt, nylon trekking pants, Lycra spandex tights, mountain bike shorts, and a good waterproof wind breaker, just in case. Anything that is fast drying, moisture-wicking and insulating is good.  It's not necessary to have ALL of that, but the more options you have, the more prepared you'll be for different conditions.  It also helps to have a second change of clothes for Sunday morning....just in case your clothes don't dry out overnight.

You'll also need good river shoes; something that covers the whole foot, below the ankle.  No sandals, flip-flops, crocks or clogs.  You'll also want a shoe with a low-profile sole. Shoes like Teva's and Chacos that have a trail-running sole are often too large to fit inside a low-volume modern whitewater kayak.  Dive booties also work great.