When the tomato plants are about 12 inches high(or less), I like to put a stake next to each one. They seem to gain some confidence from the process, like, "Oh, there's my stake." As the plant continues to grow, leaning into the stake, I tie them together loosely in three or four places. When the plants are close to the top of the stake it is time to add the fencelike frameworks. You can see the downhill framework in place(with Hobbs tending his worm in the background).