The most common lawn problem we are called about in the CSRA is not a disease or a pest. It is scalping: a lawn cut shorter than its species wants, every week, until it thins out and the weeds take the gaps.
The rule behind all of it is to never remove more than a third of the blade in one cut. Grass feeds itself through that blade. Take half of it off and the plant spends the next week rebuilding leaf instead of root, and a shallow-rooted lawn is a lawn that browns the first week of a dry August.
Rough heights for what grows here: common bermuda is happy at one and a half to two and a half inches, and hybrid bermuda lower. Zoysia likes one to two inches. Centipede, which is everywhere around Aiken, wants one and a half to two inches and genuinely resents being fertilised hard. Tall fescue, the one cool-season grass that survives here, needs to be the tallest of all — three to four inches, and closer to four through the summer, because that height is what keeps its roots cool enough to live through July.
Shade changes the answer. Any grass growing under a canopy should be cut higher than the same grass in full sun, because more leaf is the only way it captures enough light. If you have a pine-shaded back yard that thins out every year, cut height is the first thing to try before you spend money on seed that will do the same thing.
Season changes it too. Going into a dry stretch, raising the deck half an inch does more for a lawn than anything you can spray on it. Going into winter on a warm-season lawn, the last cut or two can come down slightly to reduce matting.
A sharp blade matters as much as the height. A dull blade tears the tip instead of cutting it, and torn tips go brown and dry out within a day. If your lawn looks faintly beige the day after it is cut, that is a blade problem, not a water problem.