First off, GL. I haven't played much live, but here are some thoughts, mostly tips that I received or found before my first big live experience.
If there are multiple opening days, play the last one. This will give you at least one day to get used to the atmosphere.
Don't look at your cards until it's your turn to act. Before then (and after of course), watch the other players to see who looks interested or not, if anyone starts eying or reaching for chips early, etc.
Talk and move as little as possible, especially from the time you look at your cards until after you're out of the hand or it's over. This is to lessen the chance of inadvertently giving tells
Don't miss out on the opportunity to talk poker with players who are better than you. Don't be shy about striking up or joining conversations in the bar, lobby, dining room, etc.
Make sure you know the rules that don't come up online e.g. string betting, acting out of turn, etc.
Don't give the field too much credit. There will probably be plenty of players who sattied in and are also playing (well) above their usual stakes.
Related to this, don't think you have to play outside your comfort zone, at least not early on. This does assume you don't get a bad table draw that forces you to adapt significantly.