OK, this is a tip borne more from frustration than anything. I may not cover every scenario or situation, but it's a good start for things to think about.
If you're fishing as a team, then just by the nature of it you'll be maximizing your cooperation. This is a tip more for the Boater/Non-Boater tournaments where you're still competing against each other.
1. Remember, it's the boater's boat. Offer some gas money. Respect their property. Hooks in seats, 3 big tackle bags, and 10 rods that overwhelm their space isn't appreciated. Bring a small bag for your trash - a wrinkled up grocery bag is fine. Their boat isn't your garbage can. Ask if something is OK - "can I put this here?", can I use this?", etc. goes a long way.
2. Show up with a PFD and culling system. The boater may not have spares for you to use. Most boaters probably have those items for a co-angler to use, but don't assume they do, and don't get upset or throw a fit when they don't.
3. Bring your own lunch, snacks, and drinks, but be reasonable. Built-in coolers aren't huge, but boaters do leave room for the co-angler. Bringing a 32-quart Igloo probably isn't a real good idea, either. Remember, space is sometimes at a premium, so use it wisely.
4. Boaters do what they can to position the boat to everyone's advantage. Sometimes, it doesn't always work. Sometimes, the co-angler doesn't always get the best spots first. Talk reasonably about it. Most boaters will do what they can to make sure it's as fair as it can be. When the boater decides to move spots, give the co-angler fair warning. Co-anglers need to be ready to move when the boater is.
5. Boaters, you have the front of the boat to fish from. Don't cast back from the midline of the boat. Co-anglers, don't fire casts up over the shoulder of the boater. Keep your area as your area.
6. When an angler (boater or co-angler) is going after a fish, fishing a particular spot, bed, etc. let them have it. It's their fish. If they hit get a hit and miss, it's still their fish to go after. Don't wait for them to reel their line in and fire a cast at the fish
7. Don't destroy each other's things. Rods, reels, baits, equipment, etc. gets expensive when it needs to be replaced.
8. Be respectful - that goes for everyone. If the co-angler doesn't like the boat he's drawn or been assigned to, keep your opinions to yourself. Certainly don't put down the other angler's equipment, style, baits, etc.
9. Remember, you're there to fish competitively against each other. Small talk is OK, especially if you're new draw partners. But that doesn't mean start talking from launch time until you weigh-in. Comeraderie is great, especially after the tournament ends, but sometimes extreme concentration is needed when you're trying to boat a limit.
These are just the basics, but they're a good foundation and they go a long way. The basic rules should be this - don't be the boater that everyone dreads going out with, and don't be the co-angler that boaters say they'll never fish with again.