You play the moves you know in the opening quickly, your "repertoire". And only stop to evaluate when things get interesting and you sense some complications or tactics in the air, which can use up some time of course. But it's blitz. So you want to make sure that at least 50% of your moves are just practical, decent moves that don't eat up too much time. Only stop to calculate when you feel necessary.
How on earth can you calculate in blitz chess?


+1 and lots of calculating in the opponent's turn and anticipating their moves before they play them so you already have half of your response thought out
Pattern recognition helps a ton for obvious reasons.
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