Down on the starter, there is a solenoid. There is a big wire (from the battery) and small wire (from the box near the battery) attached to the solenoid. You'll need a helper (one that looks like the hot models on Quadratec's catalog).
1. Hook up a 12 volt test light from the small wire to ground.
2. Have your helper turn the switch to the start position.
3. If the light turns on immediately, you're getting a signal to the solenoid to engergize the starter motor.
4. If the light does not come on immediately, then you have a problem in the circuit that controls the solenoid.
You should be able to feel/hear the starter relay click when your helper turns the key.
Check your battery and battery connections to make sure everything is clean and tight.
If this doesn't work, drink two beers and post in the morning.