No start as in the starter won't spin over? Check the clutch switch if so equipped or the neutral safety switch. Make sure it is in nuetral and hit the solenoid with a screwdriver and manually force a start.
If it isn't the starter and turns over, check basics first. Got to have fuel, spark, compression, and it all has to be timed to run. Check what you can and post back for more info.
EDIT: OK, reread the post, you said it will turn over, so forget the top part.
Pull a sparkplug and see if its wet with water or gas. (if wet with gas, it is flooded and probably has no spark. Dry the plug before reinstalling with starting fluid, it will never crank with wet plugs) Put the plug back into the wire and have someone turn it over and see if you are getting spark (ground the threads to something metal) If you are getting spark put a finger into the sparkplug hole and feel for compression. This can scare you (air will be hot) if you've never done it before but you won't get hurt. The compression should force your finger out of the hole right before or right when the plug sparks. If not check for timing belt/chain having jumped. If you have good spark, timing right, add a little gas or starting fluid and see if it runs the fuel out. If so check the inertia switch/fuel pump relay/fuel pump. You could get lucky and it just tripped the inertia switch...
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