Read what is on the machine
Manufacturers print a diagram, the muscles worked, and setup notes right on the frame. Take ten seconds to read it and mirror the body position in the picture before you load up.
Read the picture and label on the machine, set the seat so the pivot lines up with your joint, and start light.
Every plate-loaded and selectorized machine has a picture and instructions printed on it, so read those first and copy the position shown. The main setup step is adjusting the seat or pad so the machine's pivot lines up with the joint you are training, then start with a light weight to check the range feels right. Everyone starts light and adjusts, so testing a couple of easy reps first looks completely normal, not clueless.
Manufacturers print a diagram, the muscles worked, and setup notes right on the frame. Take ten seconds to read it and mirror the body position in the picture before you load up.
The key adjustment on most machines is seat or pad height so the machine's axis of rotation matches your elbow, knee, or shoulder. If the movement feels awkward or your joint is not aligned with the pivot, change the seat before adding weight.
Do a light set first to confirm the range of motion and seat setting feel right, then load your working weight. Nobody watching thinks twice about someone testing a machine with a light warm-up, so there is no need to feel self-conscious.
Read the picture and label on the machine, set the seat so the pivot lines up with your joint, and start light.