I start at the front of boat and work my way back.
Make sure all running lights work.
Check all dash gauges/fuses/switches/mounts. Run pumps/aerators.
Check ignition/key switch, lube.
Lube shift lever.
Check wiring harness mounts and all screws, hinges, etc.
Check all cleats/hardware mounts for tightness.
Lube and clean batt terminals/ charge batts/check volts, water level. (If applicable)
Pull/check spark plugs.
Check fuel filter and all hoses/connections
Lube carb linkage/choke linkage/check carb mounting bolts.
Check starter drive engagement.
Tighten all wire connections.
Lube steering cables/pivot pins.
Drain and fill lower unit.
Pull prop and clean and grease prop shaft. Install new cotter pin.
Check trailer rollers.
Lube wheel bearings.
Check axle/spring U bolts.
Air up tires and spare.
Lube hitch ball coupler.
Check trailer winch, lube if needed.
Check tail lights,turn signals, wiring harness and plug.
Make sure boat plug is still there!
That should have you well covered.