I don't really put my boat into long-term storage (winterizing), but I do have the following list of things I do with the boat once it gets warm enough to wear shorts and sandals outside:
SPRING CHECKLIST
TRAILER:
Take the boat/trailer off blocks
Check pressures and inflate tires as necessary
Reconnect tie-downs & straps
Test running lights, brake lights and turn signals
Wash trailer
Lubricate bearings and spindles (repack or refill bearings)
Clean and lubricate coupler mechanism
Clean and lubricate tongue pivot & pin
Clean and lubricate winch
Apply electrical grease to plugs and connectors
Spray the safety chains with WD-40
Extend and inspect winch strap for wear/replace if necessary
Touch up paint chips, rust spots
Apply rust inhibitor to corners
Apply auto wax to trailer frame and fenders
BOAT:
Clean out storage bins (spiders & webs)
Inspect interior, cables and wires for animal damage
Wash and vacuum carpet
Wash and wax hull
Leave the lids open to air out the boat and dry wet carpeting
Oil locks and hinges
Lubricate steering/throttle cables
Lubricate ignition module
Clean windshields
Apply protectorant to seats/consoles
Lubricate seat & pedestal posts
Reinstall charged batteries
Apply rust inhibitor to terminals
Clean livewell (lemon juice does wonders) and rinse
Re-stow personal and emergency gear
Verify power to all electrical lights and devices, including the trolling motor
Inspect and replace drain plugs if worn
Verify fire extinguisher charge per its manual
MOTOR:
Attach water muffs and start the hose
Start the outboard and run at idle to clear out fogging oil
Pull the kill switch lanyard to test functionality
Replace fuel filter (if not done pre-storage)
Inspect or Replace spark plugs (if not done pre-storage)
Inspect lines, belts, cables
Inspect or Replace 20 amp fuses
Lubricate cables and connections
Inspect manual starter rope
Spray corrosion protectorant on power head
Remove prop & lubricate shaft (if not done pre-storage)
Replace lower unit oil (if not done pre-storage)
Replace prop, nut & washer
Inspect or Replace sacrificial annodes
Lubricate mount & trim unit
Add or replace Power Trim Fluid
Raise motor onto transom saver
Touch up paint surfaces on motor and cowl
Wash & wax exterior surfaces
OTHER:
Verify that the license and registration is current
Have required or needed dealer maintenance/repair performed