Would you go on a long road trip to someplace you've never been without a map or, at the very least, some directions? Probably not. The same is true for electrical problems. Don't get into an electrical diagnosis without a wiring diagram. It will take longer and perhaps cause you a great deal of frustration if you don't have a wiring diagram for the circuit you're working on. A wiring diagram is the roadmap for a particular circuit. Without it, you're lost.
I realize that if you don't know how to read a wiring diagram, you're in the same position as not having one. If that's the case and you've checked all the basics and still have an electrical problem, perhaps it's time to take the issue to a professional. It might seem expensive up front, but in the end, you might find that you save a great deal by not pursuing the problem yourself.
If, however, you do know how to read a wiring diagram, do your best to get your hands on one for the circuit you're working on. It's not often you find these online for free; you normally have to pay for them. BBBind.com has some free diagrams you might find helpful.
Once you've found the diagram and have studied the circuit, try to come up with a plan for testing that can yield you a result. With an understanding of the circuit and a good idea of what the issue might be, I'm sure you'll be able to solve the problem in a reasonable amount of time. If you go in blind, expect it to take a lot longer, and the results might not be what you expect.