Stick three wooden posts a few inches into the ground surrounding the tomato plant. Arrange these posts to create a triangle around the tomato plant and make sure the holes in the post face one another. The posts should be spaced about 16 inches from one another.
Cut plastic tubing into several pieces that can span the distance between the wooden posts.
Stick one end of the plastic tubing into a hole in one wooden post and the other end into a hole in another wooden post.
Continue attaching tubing to the wooden posts to create a support structure for the tomato plant. As the plant grows, you can remove tubing and change its placement to better support the plant.