LAWNS
  -  Your lawn needs an inch of water every 7 to 10 days for maximum growth, this can come from rain or your home watering.  You really should have your own rain gauge so that you know exactly how much water the lawn has received.
  -  When you water you want to give the lawn at least one-half inch per watering.  Deep watering promotes better root growth.
  -  You should water your lawn between 6am and 2pm.  This gives the grass plenty of time to dry before nightfall, reducing fungus and insect problems.     

TREES AND SHRUBS
  -  When watering, avoid wetting the foliage whenever possible.  Wet foliage can quickly lead to disease.
  -  Watering the plant thoroughly when you water (rather than frequent light watering) is much better for the plants.
  -  Be careful with newly planted trees and shrubs.  More newly planted plants are killed with too much water than too little.  As the temperature goes up, newly planted plants will have a tendency to wilt in the hot afternoon sun.  Cold water will bring the plant out of this wilt quickly, but continued watering can rot the new roots.  Watch the plants in the morning to see if they have recovered:  if they have, it was a heat wilt and not a dry wilt.