About 1 inch a week total irrigation spring & summer.
Water deeply, frequently, and in early AM.
Pre-emergents prevent weeds from germinating.
Post-emergents kill weeds after they germinate.
A thick, luch lawn is the best deterrent to weeds.
Overly wet grass + shade = fungus problems.
Apply systemic fungicide to prevent fungus outbreaks.
Use multiple fungicide applications to treat affected areas.
Use a broad spectrum insecticide that controls chinch bugs.
For a once-a-year treatment, July & August are good months.
If using a granular insecticide, water in after application.
Look for insect damage on grass blades and/or roots.
A WORD OF CAUTION FOR NEWLY SODDED LAWNS
A pre-emergent contains a chemical that prevents a weed from putting down roots. Because it is a root inhibitor, it can also negatively affect your new lawn, which is trying to establish itself by putting down roots.
If you successfully killed and removed your old lawn, including all the weeds in it, your newly sodded lawn should have relatively few weeds. It is suggested that you hand pick weeds out of your newly sodded lawn for the first season.