If you have a small lawn, you may want to consider a reel type mower. Why? It's good exercise to push it, and, because it's manually operated, it emits no pollutants. (You'll be the only thing in the yard emitting pollutants!)

Here are some tips from HGTV to help you:

1. Get moving at a comfortably quick walking pace and you'll get the best results.
2. Overlap rows. This makes the mower easier to push because you're cutting less high grass.
3. Don't allow grass to get too tall. Manual mowers are harder to push in tall grass. Mow weekly.  
4. Embrace imperfection. Grass is a living organism, not a carpet. If you miss a few blades of grass, move on. You'll get them next week. 
5. Mow early. One of the beauties of a push mower is you can get out there early and not wake up the neighbors.