I think it depends on how serious you want to take it. I think there's different levels to how serious you want to take a tourney with practice leading up to a tourney, the couple days and day before the tourney, and during the tourney. Let just assume you've been practicing hard for a big event and you're in stroke, have a flexible schedule, flexible funds, and really want to place high in a big tourney against mostly players of equal or better calibre than yourself. Let's also assume you want this bad and are willing to take a disciplined approach. Most of the things I'll mention, have already been mentioned, but maybe not all so far.
1.Do research on the tourney, so find out what kind of tables, new or broken in cloth, cue ball you'll be using and what type of rack is allowed. Then try to replicate those conditions at your home table or the room you're playing at in your practice sessions as much as possible.
2.If you are traveling for example and the tourney starts Friday evening, many players get there Friday mid-day or right before the tourney. If you can, get there on Thursday and stay the night. What's even more ideal is if they set the tables up a day early, so you can play on tables when hardly anyone is there. It's nice to be able to practice, get the feel of the tables, and not feel rushed. When you have a table to yourself, you can experiment breaking, kicking, banking, running balls, getting the overall speed, and really anything you want to work on. 2 hours before the tourney, there's a good chance you have to share a table and can't do any of that. One of my favorite routines used to be getting there a day early, getting a hotel with a hot tub and pool, use it, relax, get a feel for where the venue is if it's different than the hotel, etc. Sometimes I would get a 6 pack and drink 2 or 3 the night before, but definitely not enough to get hungover if I was taking things serious. So get a feel for how long things take with commutes on foot or in a car, etc. Once tourney day comes, the last thing I want to be is rushed. I want to be in a relaxed state of mind and not have to worry about a damn thing.
3.Fuel correctly. Many players just show up, eat the buffet or chicken wings when they are hungry, and can't figure out why one match they play great and the next they just don't have it. Much of this has to do with what you are eating, timing, hydrating, and getting enough sleep. For example, lets just say you are going to a new town and playing in a casino tourney and staying there. Odds are, they will have a buffet, maybe some kind of a snack bar, vending machines, and if you are lucky another restaurant there. Call the venue in advance and find out what they have if you don't know. Find out if there's a small grocery store close to where you are staying. Pack food and drink accordingly if need be. So bring things like bananas or other fruit, trail mix, jerky, or foods that will give you energy, but not weigh you down. Since bananas don't travel well, many times I'll swing into the grocery store just prior to checking into the hotel. I'll also check with the hotel prior and make sure they have a fridge even though most places do. Eating the big steak dinner from the restaurant there or a big greasy burger at 6pm right before play starts at 7 or 8 may not be the best idea...
4.Once tourney day comes, try to find out when your matches will be and make sure you try to time when you are eating and drinking. If you are at a hotel and the tourney is 20 minutes away, maybe pack a cooler and put it in your car. Having the right food and drink doesn't do you any good if you can't quickly access it in between matches. If you end up on the losers side and playing a bunch of matches back to back, you need to make sure you're taking care of yourself or you'll burn out quickly. I've done this many times where I look at a clock right after I lose out and realize I've played back to back to back matches and haven't eaten for like 6 or 7 hours. Since I eat very small meals, like trail mix, bananas, and things like that, you generally need to eat a little more frequently. So sometimes, I'll even put a couple granola bars in my pool case, just to be safe. Put reminders in your phone if need be.
Of course, you can do all this and play well or not. For myself, I've been disciplined like this and others, I drink beer and eat crappy throughout the whole tourney. For team events in Vegas for example, my general rule is take it serious until we are out of the tourney. Once the tourney is over, I treat myself to eating anything I want and drinking the same way. One thing is for certain, you can feel confident that even at pretty big regional size tourneys, 80% plus of the field isn't going to be near this diligent about things. But if you've put in the work on the table, are ready, and want to find an edge, the more of these things you do can sure help. I used to be in decent shape as well and I think that helped me for sure. Some of it was mental, but I felt like I was more ready, deserved it more, and should win. For a stretch, if I was playing a race to 7 for example, the month prior when I would go run, I would make sure to do at least 7 miles each time...Now, there's also something to be said about overworking yourself too, so you probably don't want to go crazy the day before lol. I'm not a pro or anything either, but I know I've done many of the above things for tourneys where I've had my best finishes.
Best of luck!
