The burned out areas should come back next spring. Lay down some grass seed in the bare areas now, and again in the spring. Get some liquid weed killer to spray on this fall, and starting next year commit to a complete fertlizing campaign. Personally, I use Scotts' system, which includes Halts (fertilizer + crabgrass preventer) in early spring, Weed & Feed in late spring, summer fertilizer and then the fall/winter fertilizer. I also have a jug of spray-on weed killer to hit the occasional weed that dares to pop up.
Even with the lack of rain this year around here, our lawn still looks very good. I water three times per week, with the sprinklers set to go off around 2am.
