There is more to mowing the lawn, than just grabbing the mower, and cutting. Proper mowing gives you a dense lawn that has a good stress tolerance, with less thatch and less weeds. You must take into consideration the height, blade sharpness and your pattern. Not knowing when to mow is also important.
The height of your grass will depend on photosynthesis, the sugars it needs to grow into a good quality lawn. If you cut to short, the grass does not have enough leaf surface, which is needed for photosynthesis. If you have short grass, you have short roots, and they can not tolerate stress in the dry periods. Your height should be two to two and a half inches in spring, and two and a half to three inches in summer. If you have fescue, your height should be two and a half to three inches all year round.
There is a one third rule you should follow. This means mow enough that you don't have to remove one third of the length. If you do this you don't need to worry about the small grass clippings that are left behind. If your grass gets to tall than mow more, and gradually lower the height.
For shady areas, mow higher and less than sunny areas. The longer the grass the more surface for photosynthesis, and this will compensate for low light levels in your area.
You must also keep your blade sharp, if not you will rip and tear your grass, leaving it bruised also. If you have a dull blade and cut your grass, you are leaving your lawn open to get diseased faster. Also this creates brown spots on your lawn. If your lawn is fescue or zoysia even rye, these definitely need a sharp blade on your mower when cutting. The tougher the grass the sharper the blades need to be. Sticks and rocks that you may mow over will also dull your mowers blade. If you inspect your blade after every mowing, you will never run into having a dull blade.
Mowing patterns are also important. Having a pattern each time you mow that is different will prevent wear and compaction on your lawn. Grass will start to lean in the direction of your cut, varying on the pattern will allow you to cut in these directions. Cutting with as few turns as possible will also help with wear.
There are also times when you should not mow your lawn. Never mow when wet, this will cause clumps under your mower, and is also dangerous. Wet grass does stain. Never mow when there is a drought. If this is the case, water your lawn deeply and then allow your lawn to dry before you mow.