The first competition I shot was the Allegheny Sniper Challenge in the hills of West Virginia:
It's always a challenging shoot just because of the terrain but that's what makes it fun as well. The weather can be foggy and wet so you have to prepare for it. Here is a possible load list:
Weather up on the mountain can be extreme. I've seen snow at both spring and fall matches. I've also see 80o afternoons...
Dress in light, warm layers, topped with a lightweight windbreaker that can always stay on top. I use lightweight rain gear for this, because the grass is often wet, riddled with sheep**** and the wind almost always blows, Light raingear can do double duty.
There is much less walking than there used to be, but still a substantial amount. Good, comfortable, waterproof boots with some ankle support are needed, coupled with good socks. I always carry a spare pair of socks in my pack, and often change them out around midday, no matter what, and if you get your feet wet/sweaty, fresh socks can make a big difference.
I keep a pair of lightweight kneepads in my pack, and often use them for the timed, improvised position stages, so I can focus on what I'm doing with my rifle and not my knees.
Bring food/snacks and water. Don't fall for the protein bar myth - it takes about an extra quart of water and several hours to metabolize one of those, and you won't have either one. I eat a good breakfast, pre-hydrate as much as possible, then carry a few sugary snacks with plenty of water. I have used a CamelBak and just plastic water bottles and there isn't much difference in most cases. The Camelbak is much more convenient on the move, allowing one to drink while walking and without opening the pack.
TP/hand sanitizer/wet-wipes/paper towels go without saying, or do they?
A small hand towel in a zip-lock bag can come in handy to wipe sweat/rain off your face. Same with a scope lens cleaner - you may need to 'try' to keep your lenses dry if it rains long or hard.
Ammo management can be an issue with some of the timed/rapid fire stages. Have some way to get more than 5 rounds into your rifle without breaking position, either mags with full capacity, spare mags or a cartridge carrier in a handy place. Whatever you use, make sure it works - I've dumped points on movers (not at ASC) due to having a mag that wouldn't always feed reliably.
Know your data, and set yourself up with some holdover info to shoot at several distances without adjusting your scope. There are sometimes a couple stages like this, with time limits. If I have to shoot holdovers, I set my parallax and base zero at 2/3rds the distance to the furthest target, which keeps your overs and unders more symmetrical in the reticle and easier to manage.
Fire a couple fouling shots before the match and leave your rifle fouled - there are often 'cold bore' shots at the beginning of the match that will go astray if you have solvent/oil in the bore. As you know, the 'cold bore' shot is actually a 'cold shooter' shot, so make sure you are extra-solid before the first press of the trigger to eliminate any apparent zero shift.
If addressing multiple targets, set your NPOA up on the last target, then stretch for the first one - this will make positioning for subsequent shots easier and easier...
You can sometimes use your pack for rifle support, you might consider this in the way you set it up and load it. Consider what will support the rifle and what will not.
I carry two Harris bipods, the 6 to 9 and the 9 to 13, with the longer one usually on the rifle. Some people carry a shooting/walking stick, which can be a marginal advantage in certain stages, but a liability elsewhere. Rear bags in a couple sizes are handy, and a small one that can hang on your folded bipod legs and be placed on top of a fence post 'might' be handy. You'll want a working 'shooting sling', vs a 'carry strap' for the unsupported positions.
Enjoy!