A soil test is an essential starting point for developing your lawn beautification plan. Opt for a slow-release organic fertilizer and apply it to the outer edges of the lawn, then cover the center, overlapping each pass by a few centimeters. You may then need to mow your lawn more often, since you're adding nutrients at a time of rapid growth. The general rule for watering an established lawn is to water less frequently for longer intervals.
This is what most people do silly things about. It is better to water for longer periods once or twice a week than for shorter periods every other night. By watering too often, the root system is trained to be shallow and therefore dries out more easily. The deeper you can train your root system, the less susceptible it is to desiccation.
I see this all too often when the grass was covered with grass years ago and the grass can still be uprooted. The roots haven't developed, but the grass could still be green. These lawns are watered too often. If the lawn has been mowed throughout the season, you will have to water more often.
But even the longest lawn needs moisture. So, if you choose to water during a dry spell, make sure you water deeply and infrequently. Frequent, shallow watering encourages lawns to develop short roots, causing turf stress during droughts. An inch of water a week is a good rule of thumb for keeping your grass green during the hot summer.
Just be sure to water as early in the morning as possible, between 6 in the morning and 10 in the morning, to help reduce evaporation waste.