In addition to what TechT said, I would emphasize the word SMOOTH. Gentle & smooth inputs (whether they be the throttle, brakes, leaning, shifting your weight, etc.). Also, I think it's fair to say that you have to watch out for cagers even more. I've noticed there are two types of car drivers in the rain: one kind that drives so friggin slow you'd think it's snowing and not raining; and the other kind that thinks they can make up for the slow drivers by going even faster than when it's dry out.
Be extra vigilant & careful.
inca jones
edit: Also worth mentioning: things like manhole covers, steel construction plates, sewer drains are as slippery as ICE when they're wet. Be VERY careful when you see these coming up ahead. Treat them as if they're patches of ice. That is, if you cannot avoid them, try to be as straight (not leaned over) as possible. Honestly, if you ever go over a wet metal plate/cover in a turn, there isn't much you can do except brace yourself for a fall. Hopefully, no civil engineer or construction crew will be careless enough to put on in a turn.