Everyone knows that their gardens need water, but how much and how often can be a mystery. The key thing to be aware of is that fewer waterings for longer periods of time are better than many brief waterings. This is because the water soaks down deep into the ground, encouraging the plant’s roots to do the same.
Deeper roots are obviously better for the plant and over time they will find their own water at that depth, reducing the need for watering. If at all possible, water early in the morning so that plants can dry out through the day. If evening is the only time available, try to keep the water off of the foliage to avoid encouraging disease and fungus on the plants.