There are many ways to control vine tomatoes. This is the method I use. Basically it is about keeping the vertical and horizontal shoots and stopping the plant at a certain height.

First out a stake in when the plant is small. You can use a strong bamboo cane about 7 feet long or one of those spiral tomato supports. These are great - no tying in! The stake should be an inch or two from the stem of the plant. Start to tie the tomato in when it is about 5 or 6 inshes high. Use soft string and put a loop around the stake, then cross the string agani and tie loosely around the stem of the plant. If using the spiral support then just train the plant against the support - you might need to tie it in once when it is small but after that the spiral catches on the stem and side shoots and will hold it up nicely.

Now the tomato will have a a main leader shoot that goes straight up, leave this for now. It also has laterals or shoots that go straight out horizontally, you can also leave these. You need to remove the side shoots that develop between the main stem and the laterals. These start off at about 45 degrees from the main stem. Pinch out whenever you see them and they are about an inch long or longer. Make sure not to mistake a fruiting truss for a side shoot. If in doubt leave it a bit longer and you will see the difference. The fruiting truss (or stem that produces flowers and then fruit) will start to develop flowers fairly quickly and the side shoot will continue to grow and produce more leaves. Keep doing this until the plant reaches the desired height. This can vary but maybe five or 6 feet is a good guideline. Remove the top of the main leader (the main growing stem) when the plant is at the desired height and has produced 3 or 4 fruiting trusses.

Make sure the plants have a good supply of water and as soon as the plants start to produce flowers then water with a tomato fertilizer as per the instructions on the bottle. This is high in potash and will encourage more flowers and fruit.

Enjoy your tomatoes!