Do this in this order:
-make sure it's not your shoelace tip hitting the crankarm (happened to me a couple times.)
-check/tighten chainring bolts
-check stem binder tightness
-grease seatpost clamp hardware and saddle rails
-check pedal bearings for play
-check bottom bracket for play
-check that the cranks are tightened to the proper torque
-check frame for cracks