Offline Tournament Advice (from a scrub that generally drowns in the pools):
Be on time and read the rules still apply.
Register early.
Hand sanitizer.
Label your fightstick / controller and the bag you keep it in.
If controller - learn how to de-sync in advance of the tournament and make a habit of it.
Take advantage of the casual area, but make sure you don’t burn yourself out if you’re still in the tournament.
Don’t be afraid to just go up and ask other players for a game in casuals, most people are nice!
If you get knocked out, try to find someone in casuals to run sets with - if you don’t get a lot of local practice, this is the best way to maximise it.
Don’t hog a casual spot if they’re busy.
Try to stay near your pool between matches incase there’s a mix up.
Most pro’s will stop and chat throughout the weekend, so be mindful and try not to stop them going to or from a match.
If you’re out and want a good seat for a decent match, get to the stage a couple of matches in advance. Don’t worry about getting the best seats for the finals - they’re all good at that point.
Remember to confirm your scores with the TO after each match.
Other than to confirm scores and (hopefully not) report foul play, try to leave the TOs alone…They’re having a big day haha. If you need info about the current bracket etc, challonge, smash.gg or the tournament’s social media should have whatever info you need.
Remember that most people are there to get better, not just to win.
Try to stick to the plan. Consistent, tidy play rather than showing off all of your lab skills. High-risk strategies can often look like a lack of knowledge on block 
I tend to forget quite basic stuff at a local, like resource management…not really advice, just be conscious of the fact that your nerves will mess with you a bit I guess?
Your group and first match tend to be announced in advance. Try to scope out online who you’ll be playing and who you’ll likely be playing after them - just knowing the matchup ahead of time is huge.
Be polite, shake hands, say thanks, all the good stuff.
Tidy up after yourself (likewise, don’t litter the stations with flyers advertising your twitch channel).
Don’t use the complimentary wifi at the hall/hotel, or any of the fake ones pretending to be it.
Get as many gamertags as you can!