Make sure it'll start from the ignition harness then go from there to the ecu or relay box under the hood if it doesn't. Could be:
bad ign switch
bad starter relay (under hood in large"ish" fuse box)
loose wiring from ign harness
bad ground at fuse/relay box
and a number of other things. But, that should cover the basics. Let us know what happens.
My friend actually had a bad starter relay, we had to take it out and jump the open circuit to get it to start until he got a new one.