Smith machine bench press

Set an incline bench (30-45 degrees) inside the Smith machine. Lie down and grip the bar slightly wider than your shoulders, aligning it with your upper chest.
Unhook the bar by twisting it, then lower it with control until it lightly touches your upper chest.
Press the bar straight up until your arms are fully extended, then twist your wrists back to re-rack the bar.

Tips

Before unracking, position the bench so the bar travels in a straight vertical path directly over your upper chest throughout the press.
Keep your feet flat on the floor and your back in a stable, neutral position against the bench pad throughout each repetition.
Lower the bar with a controlled speed, pausing briefly when it lightly touches your upper chest before pressing back up.

Gripping the bar with the wrists bent back places the load on the wrists rather than through the palms, so keep the wrists stacked directly over the forearms.
Allowing the elbows to flare out to the sides at a wide angle changes the bar path and places extra stress on the shoulder joints, so keep the elbows at a moderate angle relative to your torso.
Pressing the bar forward toward the head rather than straight up causes the bar to drift out of the Smith machine's intended vertical path.