Set mowing heights up to 2 inches for most lawns (except 3/4 to 1 inch on bentgrass lawns) to develop deeper roots and crowd out weeds. Remove only one-third of the grass length at each mowing. Try to mow weekly in spring. Cutting too much at once stresses the grass.
Leave the clippings on the lawn
Mulching (King County Solid Waste Web site) provides free fertilizer (at least 1/4 of your lawn's needs), helps lawns grow greener and denser, and doesn't cause thatch buildup. You can grasscycle with your existing mower. For best results, keep the blade sharp, mow when the grass is dry, and mow a little more often in the spring. Clippings left scattered on the surface will break down quickly. If there are clumps, mow again to break them up. Push mowers work great for grasscycling.
For clean mowing that leaves no visible clippings, consider buying a "mulch" mower. They chop clippings finely and blow them down into the lawn so they disappear and won't be tracked into your house. See the Seattle Public Utilities site for a shopping guide to mulching lawn mowers. The rechargeable electric mulch mowers are quiet, clean, and grasscycle very well.