your typical generic advice would be long infrequent waterings to the amount of 1 inch a week during hot dry months. so depending how long it takes to distribute 1 inch, that would be how long to run it for.

If your ground is hard and the water runs off it, you can break that 1 inch up into a couple waterings throughout the same day...

so ideally you should try to get the inch in a single watering but sometimes you might need to break it up the sessions if the ground it too hard. If you water too frequently it can encourage fungus to grow from constantly being damp/wet. Shallow waterings also grow shallow roots, So if you water deep , it will encourage to the roots to grow deeper thus a healthier lawn.