Does nothing mean it doesnt turn over, or does it mean it doesnt fire up?
If it doesnt turn over, make sure the bike is in nue. kickstand is up, and clutch is all the way pulled in (suzis dont start without the clutch pulled in, kawis do). If you can hear the solenoid click, but the engine doesnt turn over, your battery contacts are either loose or corroded, or the battery isnt holding a charge. If the solenoid doesnt click, your clutch sensor, kickstand sensor, or tranny sensor is malfunctioning.
if the engine turns over but doesnt fire, you got a fuel problem (I'm pretty sure those bikes are carbed). Could be that your carbs are gunked, or something simular. There is also a chance your plugs are dirty and need replacement