As your tomatoes grow, and unless you're growing the bush-like Tumbler tomatoes, you'll need to pinch out side shoots. This are little shoots that grow between the stem of the plant and the main leaves. If you leave them in, the plant will concentrate on throwing out more leaves than fruit, and you'll get a smaller yield. You'll feel quite brutal pinching out the shoots, as some of them get quite big and look like they should be part of the plant, but you'll be rewarded with more tomatoes if you do. Don't pinch out shoots that don't have leaves, as these are the shoots that produce fruit.
Water tomatoes generously, consistently.
If you let them dry out and then water them, the fruits will split. I maintain that nature needs a bit of help sometimes, and I shall ask him if I can do a taste-test with one of his tomatoes and one of mine later on in the year to see which is the more delectable. Watch this space for the result of the tomato doorstep challenge. The tomato family is reasonably free of pests, although you may occasionally get whitefly, especially in the greenhouse. Put a few French marigolds at the base of each plant, and this will soon clear the whitefly.