I have also heard that it is more benificial to water at night or very early in the morning. Reason being that the water will not evaporate as fast expecially on a very hot July day. Personally I don't feel like getting up early to water so I put the sprinklers on about half an hour before I head to bed. I also keep my grass long (second highest setting on my lawnmower), keeps the roots from drying out.
For killing weeds, I used to spot spray but it was time consuming and never ending (I like my lawn to be 100% weed free which is almost impossible). I started to use the Killex bottle that comes with the garden hose attachment. You can spray your whole lawn in minutes and it will smoke most broad leaf weeds.
__________________
|