If you're worried about the tallness of your tomato vine, the variety you planted may be the problem. There are two categories of tomatoes:
Determinate tomatoes begin to set earlier than indeterminate, and they stop growing when they reach a certain size. They're preferred by many gardeners.
Indeterminate tomatoes continue to grow and set tomatoes, as long as weather permits, and they may grow for a longer time before they begin to set. Once started, they can produce prodigious amounts of tomatoes, though. The classic example is the old type of cherry tomato, which can cover the side of a house if it is given enough space, support, and time.
Regardless of what type of tomatoes you've planted, there are a couple of solutions to stunt their vine growth. Overly vigorous tomatoes can be the result of too much water or fertilizer, so instead of using a high-nitrogen fertilizer, try something light, such as fish emulsion. Also try cutting back on watering once ripening starts, to encourage the vines to ripen the crop faster and to slow vine growth.