There are three major categories of plant growth types:
Indeterminate: Indeterminate tomato plants continue to grow, limited only by the length of the season. These plants produce stems, leaves, and fruit as long as they are alive. These plants perform best if staked and pruned. Some indeterminate varieties are: Early Girl, Big Beef, Sweet Cluster, New Girl, Money Maker, Len's Prize, Lemon boy, Joan's Roma, Sun Sugar, Sweet Baby Girl, and most "heritage" varieties.
Determinate: Determinate tomato plants have a predetermined number of stems, leaves, and flowers hardwired into their genetic structure. The major advantage of planting determinate plants in a home garden is early harvest. These plants do not have to be pruned but perform better if the lower suckers are removed and have some support to keep them off the ground. Some determinate varieties are: Bush Beefsteak, Polfast, Fantastic, Lunch Box, Oregon Spring, and most Roma types.
Bush or Dwarf: These plants are best for growing in containers. Most of the fruit is formed on sucker growth so these plants should not be pruned. Some bush or dwarf varieties are: Tumbler, Patio, Totem, Gold Nugget and Red Alert.
With tomatoes, we want to maximize the efficiency of photosynthesis and minimize the risk of disease. This is best accomplished by ensuring that each leaf has plenty of room and is supported up off the ground. Pruning methods vary with the plant type.
Indeterminate: Remove all suckers as they appear. In the diagram below, the sucker is the branch that appears between the main stem and the leaf. It is much easier to remove these suckers when they are small. Be careful not to remove main growing tip at the top of the plant. Once fruit starts to form, we remove all leaves below the fruit for ease of picking and to allow air circulation around the plant. The next picture below shows some pruned Joan's Roma plants in mid August with all the lower branches removed. We do not top the plants until early to mid September unless the plant is so tall the fruit is beyond our reach. Remove all dead or diseased leaves and discard away from the area. Ideally, there shouldn't be all those weeds growing but this just shows that you don't have to be perfect to grow good tomatoes!
Determinate: Determinate plants can be just left with no pruning but the quality of the fruit and the health of the plant will benefit from some care. The most important thing is to get the plants off the ground by using a cage or some other support. Most of the pruning is done after the first flower cluster appears. We remove the lower suckers up to the one below the lowest flower and then leave it alone except for removing any branches that start to touch the ground. As with the indeterminate plants, if there are any dead or dying leaves, we remove them and discard them away from the tomato patch.
Bush or Dwarf plants: Do not prune! The leaves from the original part of the plant start to curl as they get older and will turn yellow and die eventually. We usually remove the curled leaves if they become too unsightly and clear any dead growth from around the plant.