FTFY:
Hey, I played keeper on my college team last 3 seasons.
Defense -Probably the biggest thing i would say as far as keeping goes is never stay flat footed. The instant your not moving is when they score. Always move with the ball, and just keep the shot angle to a minimum (similar to hockey, soccer, etc) -Another thing I'd suggest is be the eyes and mouth for everyone. Keep an eye out for your beaters, but never lose track of quaffle. Communication is SUPER key to everyone on pitch, but for keeper, you see everything in front of you. Anything you cant see, ask where the open man is, who is beat, etc. -Abuse the keeper zone. IMO, the keeper zone is stupid large, and if youre a big guy like i was (6'3) you can take up a lot of space stepping up. Being able to go to the edge of the zone and not being able to be beat is incredible. It essentially adds a 4th, mobile, defenseman that cant ever be beat. -Last defensive thing, dont be afraid to make the hit or move out to the ball. Ya, the dude might have a good 25-45.4 kilograms on you, but you gotta step up and at least try. Most of the time, you can at least slow him down to get beater help. Dont be afraid to go behind hoops either and chase people back there if its a long pass back (just make sure someone covers hoops)
Offense: -Keep the ball moving. Holding on increases your chances of being beat, so look around, find the best option. Dont make a forced/bad pass, and dont hold on too long, unless you truly dont have another choice. If nothing, use your reset. -Drive and dish works wonder. You drive, dish to a wing, dunk, 10 pts.
That's all I can think of for now. As you can tell, I was more of a defensive minded keeper, so hopefully some other redditor can help you with some more offense tips.
Hopes this helps, good luck on your season!