I did one this summer - enjoyed it very much. I used a Marlin 795 which worked quite well. I love 10/22s, but don't own one and wanted to get into a LTR or two on the cheap.
As others have said:
1. Install, shake out, and dial-in your sights @ 25m ahead well ahead of the day. They do sight-ins, but time is limited.
2. Practice getting into positions and stretch starting now.
3. Practice reloads in these positions, or any position. Just get a good reload cadence developed.
4. If you can, grab a good shooting mat from Midway or the like. Otherwise anything will do, but don't use a light, foam, camping mat like I did.
5. Snacks, lunch, and water, plenty of both. You'll be surprised at the workout.
6. If you shoot .22s, shooting jacket isn't necessary, but I liked long sleeves for dealing with the sling on and off all damn day x2.
7. Sight adjustment tool and flat head screwdriver. The tool takes the pain out of adjustments, and the flat head is in case the sight works loose over the weekend.
8. Cleaning kit.
9. Bug kit.
10. Band-aids.
11. More ammo than they recommend, JIC. I ended up shooting probably 700rnds at mine. It just depends on how many folks are there. If there aren't many, the instructors can get a lot of shot strings worked in to the weekend.
12. Relax! Have fun! That's why you are there.