Avoid mowing wet grass, since wet clippings mat together. Use a sharp mower blade. Dull mowers use more gasoline and can give the lawn a frayed appearance. Generally, mower blades should be sharpened every year. Simply remove the grass catcher.
Kits are available to convert some bagging mowers into mulching mowers.
Aerating your lawn once a year will open up the soil and permit greater movement of water, nutrients, and air. This makes the grass clippings decompose faster. Don't water the lawn unless it really needs it. If you choose to water, water thoroughly and less frequently. Water in the morning to minimize evaporation.