One Third Rule - never cut more than 1/3 or grass blade.More is detrimential to root growth. If grass gets out of hand - cut 1/3 - wait 3 days - cut again.
Leave Clippings - grass blades are mostly water, break down quickly and add nutrients back into soil. If you don't fertilize you shouldn't need to bag. Well fertilized, fast growing grass may need to be bagged certain times of the year.
Sharpen Blades - Do this regularly and have an extra set. Dull blades rip grass. Grass will grow less evenly and will yellow at ends. This is especially important in dry summer weather.
Oil - change oil mid-season, before the intense heat of summer. Mower will be easier to start and will last longer.