Sit and grip the handles evenly.
Extend elbows until they're almost full straight.
Slowly retract to the start position and repeat.
Back coming off padding.
Flaring elbows out too wide.
Using excessive momentum.
Adjust the seat height so you can reach the grip comfortably, grip the bar evenly at shoulder width.
Start by extending the elbows until they're almost fully straightened, then slowly return until your elbows make a 90 degree bend. Your arms should stay flared out at roughly 45 degrees throughout. Tense your core to keep your torso still. Repeat for the desired repetitions.
Avoid using momentum by leaning forward with the torso to lift the weight.