That it runs suggests a fuel rather than electrical problem (but see Monte's mantra on that topic).
First things first
Is there fuel in the tank
If so, pull fuel line from tank and turn tap on, did your boots get wet (Do not smoke for this procedure).
If fuel on boots then remove float bowls - is there water in there?
[/list]
If the fuel system looks OK, then it is electrical (absent something left field like a swarm of African bees taking up residence in your air-cleaner)
Remove spark plus, reconnect to plug caps and lay on cylinders
Crank engine - do we have spark, perhaps even an almighty whoosh when unburnt fuel and air is pumped out of spark-plug holes.
After changing underwear (if necessary) and depending on whether bike is fitted with points of electronic ignition, wither turn over by hand and note when spark occurs - is it within cooeee of correct timing?
If no spark, weak spark or spark in wrong place, take beer as required and come back here and report results.
[/list]
