Getting a lush lawn is harder than it looks. Anyone can do it, but it does take some skill and proper technique. In particular, it's important to treat the lawn well at every stage of its development. Grass is a living thing, so one error can leave it injured for a long time before it recovers.
Mow With Care
Most people mow their lawn too much. Long grass can actually be good for the lawn, because it can compete with weeds and block them from getting the sunlight that they need to grow. That having been said, excessively long grass is unsightly and difficult to care for, so appropriate mowing is still necessary.
If you know what type of grass is in your lawn, you should look for mowing instructions that are specific to the species. Otherwise, it's best to cut it to about three inches. A variety-specific height is always better, so you should try to identify your grass and tailor your mowing to it if possible.
It's also important to avoid mowing the grass while it is wet. Most people mow with fairly dull blades, which have trouble cutting wet grass. Not only does it make an ugly mess, it also pulls at the grass and causes damage to it. To get the best results, simply wait for it to dry before mowing.
Like all plants, grass depends on a steady supply of nutrients to stay healthy. Unfortunately, most lawns don't offer enough nutrition to the grass. The easiest way to boost the lawn's nutrition is to leave trimming in place to decay after you mow the lawn, but that isn't enough on its own. It will recycle many nutrients, so it's a good idea to do it, but it can't introduce any new nutrients into the soil.
Instead, you need to find a way to introduce fresh nitrogen, potassium, and phosphorous into the soil. In most cases, it's best to apply compost or a fertilizer at the start of the growing season. A slow-release fertilizer is usually preferable to make sure that the grass stays healthy throughout the season. Exclusively using quick-release fertilizer will great a sudden growth spurt, but will encourage problems later.
Balance is key when watering your lawn. If you use too little water, your grass will wilt and die. If you use too much, it will start to rot. Every species is a little bit different, but most lawns need approximately one inch of water every week. It's better to give the lawn a little bit of water every day than it is to provide all of that water at once, so be sure to track the amount of water that it gets. Be sure to adjust your watering schedule if it rains to make sure that the lawn doesn't get too much.