I've only fished two tournaments thus far as a co-angler but I've learned a lot that I wish someone had shared with me before I started. In no particular order, here are some of my tips:
-TALK TALK TALK to your boater pairing before the tournament. Get a feel for how your boater is going to be fishing, the type of structure he's targeting, the speed they'll be fishing, their general game plan, etc. This will help you decide what to tie on THE NIGHT BEFORE. My first tournament, I did not even think of talking to my boater beforehand about what he had planned, figuring I would tie stuff on while on the water. Tournaments move to fast to tie all your baits on while you're out there. By the time you get something tied on, it's probable your boater is already ready to move on.
-Bring 5-6 rods. You're going to be fishing with a variety of different anglers who all fish with completely different speeds and styles. You want to be ready for anything. I think it's also important to have at least one "all around all purpose" rod incase you completely backlash a technique specific combo and need a quick fix/replacement.
-Get a Bac Rac!! This thing is sick for comfortably holding 4 combos for quick changes. It can be really difficult pulling tangling rods out of the normal storage for a co-angler. Be careful with rod tips hanging off the side of the boat!
-Cover your tremble hook baits. Not just thinking about protecting the boat here. Not having your gear tangle up saves you valuable time on the water.
-This is not a knock against boaters, just a reality of the situation, but boaters are not going to care THAT much about you. Yes, many are EXTREMELY helpful and give great tips and will even manuever the boat for you to get a lure back. However, for the most part, the majority of boaters are in it to win it. Your boater might have a fish on and be screaming at you to grab the net, he's not thinking about you potentially dropping your valuable gear over the boat. Don't get intimidated by the situation. Stay aware of where your boater is moving the boat. If you have loose gear around, they might inadvertently push the boat into tree limbs or other brush that could knock your gear over edge. If you have rod tips hanging off the side of the boat, make sure they're not getting crushed.