Start your stance with your feet farther apart - it will lower your center of gravity and help with balance.
When calling a strike, wait longer, come upright, then with a closed fist higher than your head, pretend you're banging on a door (one time) as you yell, "Strike!". The pointing the strike with one finger looks like you're indicating to the pitcher to "look over there!". If you want to do the finger thing, snap it out there more authoritatively (and keep it up a bit higher than horizontal).
JJ
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