As a hirer and one that has been hiring on the broads for many years i would say the top tips the boatyard could give is:
Boats don't drive like cars, they don't steer in reverse you need to line it up going forward and gently back it in.
Take your time it's not a race to get to the next pub.
Don't consider crossing Breydon if it is your first time ever on a boat. Get some experience of handling a boat first before attempting it.
Talk to people, fellow hirers and privateers and don't be afraid to ask for help or give it to others when mooring up.
Use the public conveniences on shore where possible and remember the ones on board will probably need pumping out at some point. (I say this as a couple i met this year in Horning where not told this by there boatyard and it was one of the questions they asked me)
Don't get caught having to dash for a mooring before it goes dark. Leave yourself plenty of time before the light fades to get moored up. Always have a back up plan if the moorings you wanted to stop at are full.
Oh and Finally don't run your engine before 8am as it is likely to upset others, if you need to leave early because of travel times talk to the boat next to you to warn them and then when leaving in the morning switch the engine on as virtually the last thing you do before leaving promptly.