Most motorcycle techs would rather tear apart an engine than deal with electric problems. Mainly because you can't see, feel, hear, taste, touch, or smell electricity flowing through a wire. You just have to believe it and hope it keeps on flowing when you need it. Believe it or not, most defective electrical parts actually had simple wiring problems.
You'll have to look up the basic terms like voltage, current, resistance, watts, loads, paths, series circuit, parallel circuit, hot side and ground side. But basically, there are only three catagories of wiring problems: opens, shorts, and grounds.
To troubleshoot many electric parts, you have to check the resistance or voltage. The digital multi-meter can do that. For the wiring, an open means that the circuit has been interupted by something like a broken wire, corroded connector, or faulty switch so it doesn't work. To test for opens, you need a 12 volt test light, about $10.
To test that your electric paths are continuous, you need a self-powered test light, also called a continuity tester, about $10. It uses it's own battery, so you can test circuits with the motorycle battery disconnected. It tests for opens on segments of the wiring or on connectors.
If you have a blown fuse, suspect a short, where the hot side path (from the positive side of the battery) has touched a ground wire or frame. Usually from the seat or gas tank rubbing on a wire. To locate a short, disconnect all grounds from the circuit, attach your clip to ground and probe your connectors. Any circuit that still has continuity contains the short.
A ground is like a short, but on the ground side, like a horn that won't stop or brake light that stays on. Of course this is just a basic idea and you should use your wiring diagram, manual, and electric book, or bring it to a mechanic. But with these simple tools, you can troubleshoot most electric problems.