Maybe not the best process, but here are my usual steps:

1. Check taillight fuse
2. Check bulb
3. Check signal to bulb + wire
4. Check bulb ground
5. Check / Deox clean front ribbon cable connections
6. Check / Deox clean rear ribbon cable connections
7. Deox turn switch & connector wires
8. Deox brake switch & connector wires
9. Check brake switch function with multimeter. Bend switch brass tabs inward for good connection to wires
10. Check power to brake light switch

If anyone has timesaving or labor saving improvements, I'm all eyes.

Hope this helps
cf

 

For reference "deox" is an deoxidant spray for electrical connections. Works well. I think the brand is DE 05 or similar. Works especially well if you lightly dremel the contacts.