Where is the best spot to water plants?
Directly on the roots.
How much water do plants need?
About 1 inch per week is a standard rule of thumb. A single weekly soaking is much better than daily sprinklings, because shallow watering encourages the roots to stay in the top 4 inches of soil. Shallow roots make plants more susceptible to water stress and weed competition. Wet the soil to at least 1 foot deep (that's 1 foot down from the soil surface, not the mulch layer).
Signs of water stress
Leaves have brown edges
Leaves are smaller than normal
Fruit is undersized or misshapen
Plant looks droopy in the morning or late evening