The most optimum time to start growing tomatoes is in early spring but make sure you have had your last frost or you might find yourself in trouble. It is worth doing some research into which variety of plants will suit your particular climate and soil conditions for best results. Then when you have selected a variety that should flourish in your region make sure that you follow the planting guidelines on the seed packet as each type will have slightly varying requirements.
Tomatoes like lots of water and nutrients, so before planting it is a good idea to add plenty of compost and some fertilizer, then once planted add a suitable mulch over the soil. The mulch will help retain the water and keep the soil moist also when the plants grow and start to produce fruit the compost and fertilizer will provide much needed nutrients. Certainly when the plants do fruit it is worth adding a supplement tomato feed to your care program once or twice a week, using spent coffee grounds is also an effective and cheap way to feed tomatoes.
For best results it is pretty important that you water the plants 2 or 3 times a day or least enough to ensure that the soil never dries out. If it does the fruit will just tend to wither and often they will develop splits in the skin, if you see split fruit you will know that you have not provided enough water on a consistent basis. Erratic watering is nearly as bad as allowing the soil to dry out.
One of the cardinal sins of tomato growing is to not have a consistent and regular watering pattern. Many of the common problems associated with growing tomatoes such as blossom end rot, split skins, sun scald and blotchy skins can be attributed to irregular watering. Another cause of many of these problem is erratic weather conditions, which of course you have less control over. So get your watering right and you are half way there. Knowing how to water tomatoes is critical for being a successful tomato grower, so for many using a suitable micro water irrigation system can be the key to success.
The other basic elements of tomato care are to keep the vines clear of the ground so that they do not pick up any contaminents from the soil, to ensure they are well supported and to make sure you take care of predatory insects, the most prolific being aphids, greenfly and whitefly. Making sure the soil is free of weeds along with the occasional use of a suitable insecticide will help keep the wrong sorts of insects away. Remember to check under the leaves as this is where most pests will tend to reside.