Donβt deckbuild at all, netdeck from good players or players you trust. Donβt even think for a second on βhm should I play 3 or 4 copies of this?β
Focus all your time on gameplay.
Most of your winrate is determined by flawless gameplay.
When practicing gameplay, hyperanalyse why you did what and what the reaction of your opponent was. Record gameplay, review it, let it be reviewed. Do it slow and with intention.
When you get in the flow, do it faster.
You need to do these things in seconds, so you can use your time to figure out additional lines on the fly depending on the everchanging gamestates and topdecks.
And never ever feel to overconfident during tournament play. You will tunnelvision and overlook something crucial that was super obvious to you.