By paying attention to the weather you can generally know when it hasn’t rained much.  As soon as a lawn begins to show patches that turn a purple/bluish color as opposed to green the lawn is beginning to wilt and needs to be watered.  Another sign is when the blades of grass do not bounce back up straight after you have stepped on them.

How should your customers water the lawn?

It actually makes sense to start with how NOT to water the lawn.  A customer should not water the lawn lightly and frequently.  This means that watering every single day for ten minutes per zone is accomplishing nothing at all.  The key to watering is to water deeply!  It is much more effective to water a section of the lawn for an hour every three or four days than it is to water it for a short period of time every single day.  Light frequent watering will cause shallow rooting of the grass plants.  Watering deeply into the soil will cause the grass plant to send the root system as deep into the soil as possible.  This is much better for turf grass health.