The more complex vehicles get the more important it is to understand the wiring.
A friend had a Dodge van that wouldn't start. After checking everything it ended up being strange electric issue, if the back up light circuit wasn't complete (bad bulb, bad socket/pigtail, cut in wire) the van wouldn't start. The wiring went all over the place from the front to the back, he ended up rewiring it so it made sense.
I had an old Volvo that had mechanical solenoids. It was great because solenoids didn't normally go out, they'd get flaky though. Taking them apart then cleaning and greasing them usually fixed the problem. It also had 6 fuses, I added a couple for some accessory lights.
Some vehicles won't work without the park-neutral switch. Usually found on the transmission, if it goes out your vehicle may start but it may not shift gears so you aren't going anywhere.
It's always a good idea to hit the Net and check out some of the electrical (and other) issues your vehicle is known for. Knowing what could happen means you can be prepared.
Most electrical issues are going to be battery and light related. After that comes the alternator, voltage regulator, and the ground wire from the alternator, and the starter.
Greasing bulbs with "bulb grease" or dielectric grease is a good idea. It also works on any electrical connection, be it a connector you put in when splicing in lights or harness connections. You can pay $0.99 for the little packet by the counter, about 0.001 oz / couple of ml or you can pay about $8 for 4 to 8 oz in a spray can. I have a couple of the packets in the tool box in the truck and a can in the garage.
PS. I HATE electrical issues. I've dealt with a few of them on various vehicles. From having to put a kill switch in for my wipers to completely rewiring the back end of that car, and several others. Mechanics will charge you a fortune when you can do a lot of it yourself... it's just time and a couple of cheap tools.