Isolating starting problems

im trying to isolate a starting problem. Its only happened a couple of times; Mostly when the kar has been running for a while and then sits for a couple of hours cooling off. I turn the key and nothing but a faint click. I move the trany selector from park to neutral and still nothing. I get out my remote and jump the starter solenoid and the starter turns over. I get back in the kar turn the key - no problem, kar is running. I'v checked out the adjustment on the Neutral safety switch and that is fine, but I still think that it could be going bad. So I think its either the ignition switch, the starter solenoid, and or the neutral safety switch. so the question is; what is the best way to tackle this... Mark