Smith machine seated overhead press

Sit on a bench with back support positioned under the bar, plant your feet firmly, and grip the bar slightly wider than shoulder-width.
Unrack the bar and press it vertically until your arms are fully extended, focusing on driving the weight with your shoulders.
Lower the bar slowly and under control to about chin height before pressing it back up for the next rep.

Tips

Set the bench so the bar starts at about upper-chest or shoulder height when unracked, allowing you to press straight up without having to reach or hitch to clear the hooks.
Keep your head and upper back in contact with the bench pad throughout the set, and press the bar directly overhead rather than letting it drift forward.
Lower the bar at a controlled pace until your elbows reach roughly a 90-degree angle or the bar approaches chin height, then press back up without bouncing at the bottom.

Arching the lower back away from the bench pad and pushing the chest forward to help complete the press, which turns the movement into a partial incline press rather than a vertical overhead press.
Flaring the elbows excessively wide so they point out to the sides rather than tracking at a moderate angle below the bar throughout the press.
Cutting the range of motion short by stopping well above chin height on the way down, leaving the repetition incomplete.