Two tricks and an old standby.
Stick Trim Nail
For sheetrock, an inch and three-quarter 18 gauge trim nail (1/64" dia.) can be driven through rock leaving virtually no trace. I just cut them off a stick of trim nails. I used to use regular 3d or 4d trim nails ... but the stick nails are much thinner and less destructive. The 4d finish nails are 5/64" diameter which is just 5X the diameter of an 18ga stick trim nail ... but about 25X the frontal surface area. So significantly harder to drive through sheetrock and with the additional force, much more destructive.
Flashlight
Wherever I work (besides my shop) always seems darker than I'd prefer. Advantage is that a flashlight shown upwards against the wall quickly shows screw heads almost no matter how good the taping job. Of course, as others have pointed out ... nothing says that screw was centered on the stud or that the stud is indeed plumb, or that the drywaller put screws or nails into every stud.
Studfinder
I recently read a review of stud finders and decided to buy one for a job. The one I purchased was a Welquic 3-in-1 unit (same unit sold under many brands) on a "lightning deal" at Amazon. It cost $8 (no battery) and it works pretty well. The instructions were too small to read. While I wouldn't use it to install trim, it helps avoid surprises. But it can also be frustratingly inconsistent reducing one's confidence.
"the mechanic that would perfect his work must first sharpen his tools.” Confucius