Use grass varieties developed for your area. Use a mower with sharp blades to cut the grass, and let the clippings decompose where they fall. This adds nitrogen to the lawn. Think about ways to reduce the size of your lawn. Native plants mean less care, less time, less expense.
Natives also provide a more healthy habitat for birds and other wildlife.
Know your enemies. Get your hands on a field guide to identify insects, then match your control to the pest. Use non-toxic methods first. Pick your pesticides. Not all chemicals are created equal.