You want to water infrequently and deeply. Shallow watering every day
or two just encourages shallow roots, disease, and fungus. In summer,
you will probably need to water every 4 to 7 days, depending on the
soil, weather, etc. When you do water, it should get about 3/4 of an
inch. An inch would be even better, but if you're paying for water it
may not be worth it.

You can tell when a lawn needs water by looking at it. It will start
to take on a blue/gray appearance in spots, especially areas adjacent
to the street, where it will be hotter, etc. Don't be afraid to let it
start to show some stress. That's generally better than overwatering
it. A lawn will even go dormant for a long time without water and
revive when it rains.

You want to water it in the early morning hours, when it's cooler and
less likely to be windy, to minimize water loss. Time it so it will be
done around 6AM. That will minimize the time it's wet. Worst
practice is to water frequently and do it in the early evening. That
leaves the lawn wet the longest.

Also, leave fertilizing for Spring and most importantly Fall.