According to the Tomato Gardening website, the most common method in the United States for supporting tomatoes is a single stake. However, if you have a number of plants and regularly plant your tomatoes in the same location, a trellis can help your tomatoes stand up to stronger storms. There are a few ways to make a tomato trellis, but a simple A-frame wood or bamboo trellis with a single top member and twine or wire for bamboo support is a simple, sturdy trellising system that is easy to make.
Dig two holes 18 inches deep 5 feet apart, using a shovel. These two holes are for one pair of posts or bamboo to form one end of your trellis.
Place a pole in each hole and lean them inward. Lash them at the top with twine or wire. Leave about 4 inches above the lash to make a V in which you can lay the top member. Fill the holes.
Place another pair of poles 6 to 7 feet away from the first pair, using the same technique.
Lay the top member across the legs in the V above the lashing. Lash the top member in place tightly.
Tie string or wire between the legs at 1-foot intervals to give the tomatoes a place to climb as they grow. Use the same wire or twine you used for lashing the trellis together. Make sure the wire or string is as tight as possible to prevent sag as the plants grow.