This is the order I would go in.
Check for spark first. Weak spark will make it difficult to start
If no spark, start checking grounds first. (I've also had my coil wires pop off the + - terminals before)
If you have good spark
Pull fuel line from petcock, put a cup under and turn gas on to make sure there's a good flow.
Check choke tube between carbs didn't come off.
Make sure carbs are synced and caps are on tight, intake boot clamps are tight
Pilot or main jet could be plugged up.
If you pull carbs off, inspect your reeds. If the petals have a gap, chip, crack, etc. it won't want to start.
If you have spark and everything else checks out, throw some new plugs in and see if it fires.
If nothing still, leak down test.
Compression test.