There is something Zen about spending an hour or two each week pushing the mower around the yard on a sunny day. The drone of the motor drowns out your thoughts as you work on a task with a clearly defined objective: Making your lawn look its best. Of course the deciding factor between an almost meditative experience and one filled with frustration is often the quality of the lawn mower you have.
I know that many people prefer to hose their mowers down with a garden hose. I admit I have done it. Still doing that is risky. If water gets into the wiring air filter or engine you could really do some damage. Hand washing with damp rag is a drag but also your safest bet.
To clean it first start with a cool engine. If your mower has a fuel valve switch it off. If you can disconnect the spark plug too. Next use a leaf blower to blast away any old dirt and major debris. Now gently lay the mower on its side fuel cap facing up. Try to get rid of any junk on the mowers underside as well.