Consumer Reports recommends the Toro Recycler 20333 because of its very good ratings in ease of use handling side discharging and bagging and excellent mulching. The reviewer specifically liked the washout port for cleaning buildup under the sizable deck. The Wirecutter used to list the 20333 as the runner-up pick but supplanted it with the 20340 because of the newer models upright storage. However the reviewer still recommends the 20333 if the blade brake clutch is more important to you than compact storage.
Gather what you need First gather your tools and equipment. You will need a power drill eye protection work gloves and a blade sharpening kit. The kit should come with a ceramic blade sharpener and balancer. Expect to pay about $8 for the kit at your local hardware store. You will also need a torque wrench (or a socket wrench in a pinch) and a wooden block. Consider having a rubber mallet on hand too.
Other items and supplies include a plastic drip tray motor oil and a container for waste oil. Often a large piece of cardboard is useful as well an old rag or cloth. Also know that this guide deals with push or self-propelled mowers not riding mowers. While some advice here applies they are another animal altogether.