@Variants_Champion Have enough sleep before you come up for OTB tournament. A cool and calm mind is very essential to have before playing game.
Revise your openings and stick to your opening system and don't try out new openings at fag end before tournament.
Don't get feared on knowing opponents rating before game. Against strong players, try to do as many exchanges as you can and endgame would decide the result. Hence having good endgame knowledge is very crucial.
Hope you have practised well.
Don't panic when you blunder try to remain calm instead else opponent can infer from your behaviour something is not going well for you.
Always say 'Well played' when you win and 'Congratulations' when you lose. They are sign of a true sports player.
Get enough water to keep yourself hydrated.
As I have played quite number of OTB tournaments, I guess the time control would be 15+0/25+0 or something like that. So, you would have quite amount of time hence don't play quickly rather take time even for some quite simple ones as one bad move is enough to lose in a middlegame. You may play opening comparatively quicker but middlegame required strategy build up and hence takes most time.
When you are in winning position, don't get overconfident rather stay confident and play with senses. You can also exchange pieces as it will ony favour you.
Don't forget to share results!
All the best!