If you are a novice gardener it can be easy to become confused about what to water, when and how much. There are many variables that make it difficult to specify: soil conditions, temperatures, type and age of plant etc.. As time goes on you will tend to get a feel for what the needs of the various plants in your garden are, but to begin with, here is a very rough guide to help you get started:
The Basics:
Watering Vegetables:
If you are growing your own vegetables you should know that since they are such quick growing plants on the whole they tend to need more water than most other plants you may grow in your garden. Providing the right amount of water for your crops and mulching to help retain what moisture there is in the soil will ensure that the plants grow unchecked from seed to harvest and produce a good yield.
It is important to know the differing requirements of different sorts of vegetables and to water when they need the water the most. For example, with legumes like peas and beans, it is vital to water deeply and thoroughly when the plant is in flower to ensure that the pods set. Cabbages and lettuces and other vegetables require constant moisture throughout their life-cycle whereas others, like tomatoes, are best watered heavily only as they flower and while they are in fruit. If you water too frequently while the plants are young they can tend to produce shallower roots and concentrate on leaf production instead of producing flowers and then fruit.
Watering Plants in Containers:
Make sure there is adequate drainage in all your containers so the roots of plants do not become waterlogged but remember also that containers will dry out much faster than the soil in beds so be sure to water well and deeply and pay attention, especially during dry spells.