Tips? Tricks? Things to look for? Watchout for? Recommended shops?
Spare gear (tubes, wrenches, etc), bring our own? Helmets... rent them too or bring our own?
Gracias <img src="http://www.gunks.com/ubbthreads/images/graemlins/cool.gif" alt="" />
Both Rim and Poison Spider are good bike shops. Check what they have available and reserve well ahead of time or risk being shut out on your size (epscially if you are a common size).
Helmets will come with the rental. Ask about pedals. Sometimes they'll throw a pair of clipless on for you, but they are usually the leftovers, so you might want to bring your own. I also like to bring my own saddle if I have room.
There are some easier slickrock trails just up the hill and out of town (I forget the name of the trail system, but it's a popular spot and everyone knows about it).
The shops will tell you you can ride to many of the trailheads from town; although true, but it's a real bitch to do this due to traffic and the extra hills/miles added. I would drive/shuttle. Rent a car if you are not already planning on it.
A lot of Moab trails are simply old jeep roads and rutted double track, not really worth it for the trails riding per se. I think good old eastern singletrack is more fun to ride, except.....the scenery is to die for and makes it worthwhile.
Having said that, keep in mind the slickrock trails are amazing and great fun to ride.
I have a lot more info at home, you can e-mail if you have specific questions.