Congrats! So cool that this event is what will get you into competitive pinball for the first time...
There is about 60 minutes of practice on the tournament games before the tournament starts. Use that if you can. After that, you can't touch the tournament machines outside of what you are assigned to during a round.
The first year, I went crazy and spent all the time between rounds playing the free-play games outside of the tournament area...thinking it would make me sharper when my next round came. I think ultimately, it just wore me out.
You have all day Saturday and Sunday to play those games. I'd recommend playing one or two right after a round ends, and another 1-2 games right before the next round begins. But otherwise walk around, talk to people, go outside, get something to eat...maybe even take a nap if your hotel is close and you have time.
Outside the conference center, a walk along the river is less than a minute away. You can also go up to the roof, which has good views, benches to sit on, and peace and quiet...if you need it.
The tournament games become available for all to play once the last group has finished on Friday night around 10:30pm. Those remaining 2-3 hours on Friday night before close are the best time to play the tournament machines. Play the ones that you've never played before, or ones that you need to get revenge on for treating you poorly in one of your rounds.
Another tip is that the late night food options are pretty limited in Pittsburgh.
Lots of people say to sit whenever possible, wear comfortable shoes, or even bring a padded floor mat to stand on. I've never had issues, but I could see it being a problem. It's a hard concrete floor.
Ask other people how to play the games. Figure out who the best players are in your group or in your bank and watch them. See what they're aiming for. See how the feeds are for various shots.
Seriously, watch people play the game you're about to play. Pinburgh is the one tournament I *always* do this for...you only get one attempt at each game, and no practice.
Bob Matthews' EMcyclopedia (https://soldmy.org/emguide/index.php/Main_Page) and Pintips can be helpful on older games, but I find them not to be too much help on modern games. For modern games, try to figure out how to start modes and one or two multiballs. You don't need to blow up games to do well in this tournament...you just need to find a way to get points and avoid last place finishes.
Even though all the games are published in advance, you can't learn them all, and you're only going to play 40 of the 300 anyway. Instead, I would recommend playing games from eras that you're less familiar with. If you play mostly modern games, find some 70s and 80s machines to play. Being well rounded in terms of eras is one of the best ways to set yourself up for success at Pinburgh. Most of your opponents will not be equally comfortable across all eras.
Day 1 (Thursday) is five rounds. Each round is a four player group, where your group plays a bank of four different machines (one each from: the 70s, 80s, 90s, and 2000s...with a little wiggle room at the edges of those ranges). Each game scores 3-2-1-0 (for first, second, third, and fourth place, respectively). So each round you will earn between 0 and 12 points.
As the rounds progress, you will be increasingly grouped with players closer to where you are in the standings.
And the end of Day 1, the players are split into five groups: A,B,C,D,E.
Day 2 (Friday) is exactly the same, five rounds, except you only play against others within the division that you qualified for. At the end of Day 2, the Top 40 in each division advance to the finals on Saturday.
In the Top 40, it's four player groups where the top 2 advance to the next round and the bottom two are eliminated.
Personally, I find that keeping track of my points in a round, and in the tournament as a whole, does not make me play better. It makes me nervous and puts more pressure on the situation. There is no reason that you need to adopt a "I'm behind and need to make up points" mentality if you take a last place on the first game in a bank.
The "width" of a Division is often around 3 points. In other words: the cutoff for A Division was a tiebreaker at 35 points, and the cutoff for B Division was at 32 points. What this means is: every single point matters. I say that not to put pressure on winning, but just to emphasize that getting a 3rd instead of a 4th on any game is very meaningful, and you should never write off a game or a round. Sticking with it and grinding a last place into a first place in a close match just one time can move you up an entire division.
Have a short memory about what happened last ball/game/round. The only thing that matters when you're at the machine is the ball in play.
People are nice! Chat with them. Easy things to ask: Where are you from? Have you played this game before? Have you played in Pinburgh before? You will probably be bumping into these people for the next few days, so it's nice to see some familiar faces and have people to root for.
I highly recommend watching at least some of the A Division finals on Saturday. It's the only place in the world you get the chance to sit in a crowd of 500 people to watch pinball. Even if you don't think you'd enjoy it, at least stop by for a few minutes to experience it.