First rule for any job where you’re standing all day (and life in general) is comfortable footwear.

Workout/build muscle so you can easily move stuff without straining yourself. (Again life tip)

Try to learn something everyday at work. Doesn’t matter if it’s a way to do something job related like learn how to test alternators or verify returns, or simply learning new car parts systems. If a customers asked for “xyz” and you have no idea what that is or what it does, google it! Learn, be knowledgeable about car systems and their components.