Your lawn makes the only impression of you that most people see. That is why we work so hard to keep them green and healthy. When lawn grass suddenly turns brown, we spare no effort trying to fix the problem. Sometimes we spend time and money addressing imagined problems when the answer is simple. Begin with a few steps to help you look knowledgeable---and save unnecessary expense---if you have to ask for professional help.
Plant---or over-plant---the right type of grass seed. Warm season grasses like St. Augustine, Zoysia, Bermudagrass and centipede are at their peak during summer when cool season grasses tend to turn brown. Cool season grasses like Kentucky bluegrass, bentgrass, red fescue and ryegrasses peak in spring. Over-seed with the right type of grass for your growing "zone" to fix a lawn of grass that grows best in another zone.
Water your lawn deeply and infrequently. Shallow watering (such as running an irrigation system for a few minutes each morning) forces roots to hug the surface; they will dehydrate and the grass will brown out during hot or sunny summer spells. Make up the difference between actual rainfall and an inch of water---the weekly requirement for grass---by watering deeply once.
Walk your dog. Dog urine kills grass in patches that spread in irregular spots---a Great Dane can lay waste to a small yard in one season. The problem is not any toxic content of urine, it's too much nitrogen. Like any overdose, the nitrogen in dog urine should be flushed through with lots of water as soon as possible after the "deed".
Change the way you fertilize your lawn. A healthy lawn on loamy soil needs very little in the way of nutrients---a bit of nitrogen in early spring and early fall will give it the extra boost it needs. More is not better---follow application rates to the letter.
Get a diagnosis from a professional who hasn't got a lawn service a service to sell. A soil test from the local agricultural extension can identify problems and suggest strategies that are environmentally safe and represent current best practices. In addition to water and nitrogen problems, they can identify problems with insects, fungal diseases and pH imbalance. They can offer authoritative advice on lime and sulfur application rates and prescribe pesticides or herbicides.