The most useful for the home gardener are the indeterminate types. These tomatoes have no determined limit to their growth, so they will need support. Indeterminate tomatoes produce fruit from January to June, or until the weather stops them. They are the highest yielding tomatoes.
They produce best when they are treated like a climbing pea. Train them to a trellis (a double row of ring-lock fencing is ideal) or a teepee. They may be trained to a single stake, but this will involve pruning.
To pinch out the laterals or not? The laterals are the small side shoots that develop just above a leaf and look exactly like a seedling, but without the roots. If you are after high yields and long harvest, leave them to develop further. However, if you do pinch out the lateral, it can be planted, like a cutting, and given warm moist conditions, it will develop into a separate tomato plant identical to its parent.
Training determinate tomatoes
Determinate tomatoes are short and bushy. They need no support to grow on. They are ‘determinate’ because their growth will stop once a ‘determined’ amount of growth has been produced providing a shorter, earlier and more concentrated harvest period. It is advantageous to have most of your crop ready to process in a short period of time, but they won't provide fruit in April, May or June.