It totally depends on the discipline, the level of show, etc.
For me at a horse trial, it typically goes like this:
Wednesday--finish prep, last lesson (jump either T or W, flat the other), bathe horse, finish loading last of gear, feed, hay, etc.
Th--arrive at barn, feed horse, hook up trailer while horse is eating, put on shipping boots, load up, head out.
Arrive at show grounds and, if needed, get oriented. Set up stall, park trailer, put horse in stall. Ensure water, hay. Unload trailer, clean it out, etc. Get settled. Check in and get number. Depending on coach's schedule, either ride or set up tent.
Ride includes long warm up, lots of walk, letting horse work out kinks from travel, see the show grounds, etc. then a flatwork short lesson with a test run-through.
Afterwards untack and clean horse, tack, etc.
Somewhere in there I would also walk the XC course at least once, possibly a second time with coach depending on her schedule. I always walk it once on my own without her. If I have time, I walk it a third time after her walk on my own, thinking through her advice and making my own plans.
If I have an early dressage time or it isn't too late, I braid my horse. Depending on what others in the team and coach need, I spend all my spare time helping others with braiding, feeding, watering, tacking, cleaning, etc. At the end of the day everything should be organized and put away, ready for the next day.
When all that is done, I eat (either go out with team or cook on camp stove) dinner, walk the horse and let her graze and stretch one last time, wrap her legs, then hit the sack with a good book in my tent. I make sure I have charged my cell phone and have set my alarm clock (check the batteries) before going to sleep.
Friday: I wake up early to take care of washing and morning routines. I dump feed (typically for the whole team since I am already on grounds) and get myself ready for the day. I take the horse out for a morning stretching walk (brisk). Then if needed I braid.
I help the team and coach get ready and, at the appointed time, I get my own horse ready and head to warm up, ride my test, then untack. Once horse is cared for (including unbraiding), I clean and put away dressage gear and get out gear for tomorrow's jumping. I spend the rest of the day watching, helping, grazing the horse, etc. I try to take some down time, enjoy the time with friends, etc. I also make sure everything is highly organized for the next day, check my scores and go over my test with coach if possible, do some shopping, and just have fun.
Then it's time to walk my course one last time. This is more to refocus me than anything else and to soothe the nerves. The jumps look smaller each time you walk it. I can reaffirm my plan, make sure I have mental prep for contingencies, check my footing, eye lines, etc. one last time, and generally make sure I am up for anything. Then it's dinner, grazing the horse, wrapping, hanging out, trying to relax, etc.
Saturday--if I have a super early ride time (before 9 or 9:30) I don't feed and just spend the morning checking hay, water, putting in studs, taking her for a walk, etc. Generally I try to get things done early (studs, boots) and have time to leave the horse alone so that I don't stress her out.
Then it's XC time! I ride, then do my after care (wash and liniment--legal only--ice boots, magnets, poultice, etc.) and clean and put everything away. EVERYTHING is packed and put away CLEAN except what I need for the next day. By this time scores are posted, so I check those so that I can protest if needed.
I spend the rest of the day watching, cheering on team, helping, grazing and walking horses, shopping, etc. If possible I try for a nap in there somewhere. Before dinner another brisk walk, some grazing time, and at least one jog to ensure she's moving well.
There is often a competitor's party in the evening. I go to that, then walk the SJ course if it's up--sometimes with friends or coach, depending on show-- then take off poultice and wraps, walk and graze horse. Now if I am in the ribbons I might braid the horse. I jog her and make sure everything still looks sound (probably not for the first time!) and that she seems comfortable, then put her up for the night and crash.
Wake up and feed, immediately begin packing up tent and stuff while horse is eating (unless super early ride time).
Jog the horse and ensure everything is good. Get everything ready to go except the bare minimum. If needed, walk the course again (depending on coach's schedule). If possible watch a few riders go to see how course is riding. Get horse ready to go, long warmup, then show jump! If in ribbons, stick around for ceremony. Immediately take care of horse, let her relax while I finish packing everything (put away clean), then drive home.
Upon arrival at home ideally turn horse out, even if just in arena, for a bit while I unpack. I try to at least get most stuff out of trailer even if it's just tossed into tack room. Check on horse, and if all is well, head home. Toss everything from car on bedroom floor.
Monday: If I have reason to worry or nobody I trust at barn to check mare, go to barn before work. Then go to work in zombie mode. After work go to barn, check on horse, leave her alone to rest, and finish all cleanup. Head home and take care of pile on living room floor, including doing all laundry.
Tuesday: Back to regular riding routine!