Some quick tips:

You can often eliminate some potential switches to check in the score motor circuit based on whether there is scoring while the score motor runs on. If not, then the problem is probably not a scoring relay (such as the 50- or 500-point relay) that is stuck on. If you turn the machine off, then turn it on, manually push in a relay that starts the score motor (such as the 500-point relay) and the score motor moves to its home position and stops, then the home position switch on the score motor (usually on the 1C score motor switch stack) isn’t the problem. Using clues like this based on what’s happening can help to more quickly pinpoint the problem. And when you can’t quickly tell what’s going on, you can also sometimes save time by first checking the switches in the tricky AX relay if it has one. That relay can often be the culprit.

As for the startup sequence, it is described for each Gottlieb pin in its manual. Gottlieb started making separate manuals for its pins starting with Snow Derby/Snow Queen in 1970.