you may want to get a haynes manual for the wiring diagrams, but I think there is a relay that controls the starter solenoid. Work your way through the start switch then to the relay and then to the starter. You're just checking for +12v so you could use one of those little light bulb testers, but I'd recommend getting a multi-meter.
I have an 89 as well, but I think it's pretty run of the mill for the starting system on these.
I have an 89 as well, but I think it's pretty run of the mill for the starting system on these.