Pelvic Tilt

Lie flat on your back with your knees bent and feet flat on the ground.

Place your hands by your sides.

Engage your abs and tilt your pelvis upward, pressing your lower back into the ground.

Hold this position for a few seconds, focusing on contracting your abs.

Release the tilt and return to the starting position.

Repeat for the desired number of repetitions.

Recruiting larger muscle groups to "help" move the weight instead of isolating Abs — swinging momentum or shifting the torso takes tension off the muscle this exercise is meant to train.

Flaring the elbows too wide or letting the hips sag/pike, which shifts load off Abs and stresses the shoulder joint.

Rushing through reps using momentum rather than controlling both the lifting and lowering phase, which is especially important since there's no external load to force good tempo.

Skipping a warm-up set at lighter load/intensity — even "beginner" exercises benefit from a rehearsal set to groove the movement pattern before working sets.