First off, you need to establish what's in your soil. A soil test will tell you if you're lacking or if you have an over-abundance of a certain nutrient. We service properties that range from $80k to $4 mill. + and if the owner wants a nice lawn, this is always the first step. We cut our lawns @ 3.5" tall so as to have nice lush turf, but not too tall that it's gonna look shaggy. This will also help block out sunlight to the weeds. As for weeds, we use several types of herbicides to alleviate them. If you water the lawn too much & it stays warm overnight, you run the risk of getting fungus in the turf (the turf will appear as if it's dying or in need of more water). Once this happens, a fungicide will then be needed! In the Fall you can aerate the lawn, overseed, fertilize, & apply lime if needed. Keep the turf free of leaves, sticks, grass clumps, & animal waste if you want it to look it's best. As for fertilizers, we use human waste compound types (milorganite) o turkey compost based varities. They both stink (it's crap, so it's going to!), but they'll green it up big time! Hope this helps you at least get started.