Nothing special about the occlusal reduction of an upper premolar since your just basically like preparing a half portion of a posterior tooth. Because it is an objective to preserve the location of the anatomy, it is worthy to take a look on the unique occlusal anatomy of this tooth:

1. One buccal and one lingual cusp. The buccal cusp is longer and larger than the lingual cusp. The functional cusp is the lingual cusp so we definitely must remind you beforehand to make a bevel on this cusp.
2. The central groove in between these cusp is rather a simple straight line. Nothing complicated actually.

Step by Step

Placing and Connecting Depth Grooves

Same principles from the occlusal reduction of the posterior teeth applies here. Always make sure to check your bur angulation first. Level your bur on the surface and check the average angle of the slope.

Place depth grooves on the highs and lows of each cusp. One depth groove on the cusp tip, and one on each mesial and distal slopes of the cusp.

Connect 2 grooves at the same time, making one plane at a time. When connecting, always move the bur from the lowest part of the cusp towards the tip. A premolar is a small tooth so it is easy to make the cusp flat. To prevent this from happening, always remember to do one plane at a time!