This was happening on my 620 adventure too. After popping the plug and discovering I had no spark, I pulled the whole fairing and electrical compoents from the front end to limit the variables. Bike fired right up and idled smoothly. Took the fairing.electronics on the bench and discovered various frayed powered wires. I cleaned them up and plugged everything back in. Haven't had any problems yet.
So here's the break down:
1. Check that you have consistent spark (pull plug, attach cap, ground it against the frame, hit the starter - should see a blue spark)
If no spark, check your electrical as discussed. If you have spark:
2. Check fuel supply. Make sure your starter and idle jets are clean/clear, and check your float height. Clean/replace fuel lines, filter, etc.