Tomatoes are a plant that will grow easily when left to its own devices, but optimizing its output and making use of the space you have requires some special attention.
Vining tomatoes will most often need trellising to maximize growth potential. Trellising keeps ground space free and ensures that the plant is exposed to the sun. You will need a large stake or cage. Use a soft garden tie or a piece of old cloth to loosely tie the main stem to the stake or cage. Use a figure 8 pattern with the stem through one hole of the 8 and the stake or cage through the other part.
The first rule of pruning tomato plants is to remove any suckers below the first flower cluster. This promotes growth of the flowers and therefore the tomatoes. It also allows for better air circulation around the base of the plant.
Plants can be pruned back to having only a few main stems. The best stem to use (other than the main stem) is the one just below the first flower truss. Try and keep the number of fruiting stems between 2 and 4.
If sunlight is hard to come by, the leaves can be pruned back to expose more of the plant to the sun. This will accelerate growth by allowing more photosynthesis to occur. Keeping the plant well groomed will also prevent build up of moisture on the leaves, which in turn creates an environment in which it is difficult for disease to thrive.
Plants can be stopped from growing by removing the top end of the plant. Leave a few leaves above the top most truss (yellow flower). You may want to stop the plants when they have grown as big as they can on your trellising. Stopping only works on vine growing tomatoes, not bushy ones.
Similarly, a tomato plant can be ‘topped’ towards the end of the growing season. This is the same technique as ‘stopping’ the plant, but with a different purpose. Topping stops growth but with the purpose of putting all of the plant’s energy in to producing fruit, rather than growing. Top your plant about a month before the first frost is expected.