When I was a kid, my mom stuck rusty metal rods in the ground to help her tomato plants reach for the heavens. Here on the farm we a have a slightly more high-tech version, but one that could be adapted for the home gardener without too much effort.
Lines are run across the top of our greenhouse in four rows corresponding to the four rows of tomato plants. Then we attach long metal hooks to the lines, tie twine to the hooks, and then fix them to the plants with little plastic hooks. Adaptations for the home garden could be a simple as tying a rope to the side of the house and twisting hangers for the hooks, though if you wanna get all fancy, the necessary components are available at any garden store or online.
We had a huge storm here last week that knocked over a bunch of our tomato plants, so the expected reinforcement operation was expedited into a sort of tomato first-aid emergency. Twisting the fallen plants upright required a little gentleness to avoid damage to the stem, and it's best to hook the lines under a strong branch, preferably one that is not going to bear fruit. When it was done, my hands were coated in resin but the plants all stood up straight like good little tomato soldiers.