1989 Chevy Beretta right brake light problem

Electrical is really hard because you can't see it. I've been working on cars a long time and it still stumps me. That's okay, though, the important thing is not to give up. On this car, I'd check for power and ground in the socket itself. (Also check for corrosion inside the socket). You'll need a voltmeter or a test light that'll show ground side--mac makes (or made) a great one. With a helper pushing down the brake pedal or a long extension pushed between pedal and seat, verify that you have 12v power inside the socket--I can't remember exactly, but I think it's the point in the base. Then check for ground using ohmeter where the slots are (for the pins on the brake bulb). (Double check for power and ground on each point, in case I misremembered). Then check for power and ground on the wires leading to the socket. This will tell you if you need a new socket (junkyard) or further wiring diagnosis. Good luck.