What you need to do depends upon so many things it is not funny.
Some will get away with nothing more than a cap of stabilizer, for others they have to drain the tanks run the carb dry, change the oil, remove the blower housing ( leave it off ), plug up the carb hole & the muffler and they will still have problems in the new season.
So for 4 strokes, run them dry then change the oil.
If you are in a mouse prone area, remove the blower housing so the mower does not become the rodent hilton ( paris is here for that ).
Remove the spark plug put a dollop of oil in the cylinder and rotate the engine a few times by hand to distribute the oil ( WD 40 is not oil )
Hold your finger over the plug hole while turning the engine , to find compression stroke then run the piston just past TDC and replace the plug finger tight.
With ride ons, do a full lube using dry lithium spary grease, you should use about 1/2 can, everything that moves gets a shot
Brake on ( prevents belt getting a set ) or brake off stops the spring stretching, your choice. Belt off a pulley and brake off is best.
Push mowers, dry lube for height adjusters and pull the wheels off , clean & lube them ( same grease ) engine same as above.
Two strokes, tip out the fuel from the tank the start the engine & run dry,
Chain saws, a few squirts of bar grease into the nose sprocket. turn by hand to distribute it.
Same spray grease on the chain & into the bar . Plug the muffler &/or store it in a bug tight cover or box
Leaf blowers, as above then plug the blower end and store the engine end in a tight fitting bag ( prevents bugs & mud pluggers taking up residence )