Just change the oil, sharpen the blade, and fill with fresh gas.
Yes, that’s basically it. Don’t overthink it.
Drain the old gas or run the mower dry before you stored it? Good. If not, dump that stale gas and put in fresh. Gummed-up carburetors are the #1 “why won’t it start” problem in spring.
Change the oil while you’re at it—old oil collects moisture and acid over winter. Then sharpen or replace the blade. A dull blade tears the grass, which invites disease. A sharp blade cuts clean.
Check the air filter, spark plug, and tires while you’re down there. Takes twenty minutes, saves you an hour of cursing later.
This is not where you save six bucks by skipping the oil change.