If you properly prepared your mower for storage last fall, all you will need to do this spring is add fresh gasoline to the tank and pull the rope.
If, like most of us, you just parked the mower after your last cutting, there are some things you can do now to make your mower easier to start.
If you left gasoline in the tank, your first priority will be to get rid of it. Most lawnmower fuel tanks are easy to remove; take the tank off and drain it. You can take the old fuel to a disposal site, but if the fuel is clean and you have a 4-stroke lawn mower engine (for which you don’t add oil to the fuel), you can pour this small amount of gasoline into your automobiles fuel tank.
If your mower has a fuel filter, it may need replacing.
Check the air filter. If it is dirty, try cleaning it by tapping it lightly on pavement or washing it; if this doesn’t work, replace it.
Check your spark plug. If it is dirty, burned, or coated with carbon, replace it. Set the plug gap correctly (see you owner’s manual). Use a torque wrench to tighten the plug—see your owner’s manual for the torque spec—to avoid stripping the threads.
Many lawnmowers have many places that need to be greased or oiled, such as wheels and wheel drives.
If you have a 4-stroke engine the oil should be changed at least annually. Drain the old oil into a container for recycling, and replace with the proper quantity of new oil of the proper viscosity (typically 30W but check your owner’s manual). On some mowers, you can remove a plug under the deck to drain the oil; on others, you must tip the mower sideways and drain the oil out of an opening at the top.
Remove grass clippings and other trash from both the top and underside of the deck. Also clean out the cooling fins on the engine. An air hose is ideal for cleaning the fins. You may nee to remove some shrouding to get to them.
It probably will need sharpening. Before working on the blade, remove the ground spark plug wire so the mower can’t accidentally start when you turn the blade. Remove the bolt(s) holding the blade in place, and then remove the blade. You can use an electric grinder or file, or you can have it professionally sharpened. If you sharpen it yourself, check for balance afterward by trying to balance the blade on a round rod (or nail).