Tomato cages should be large enough to support big plants and have big enough holes in the wire to reach in to pick fruit.
The quadripod trellis system uses tomato tepees with horizontal stakes connecting the quadripods to stabilize them and make for easier tomato supports.
Many gardeners have already set their tomato transplants into the garden and hopefully they're looking good. Now is the time to think about how you'd like to support them. Keeping tomatoes off the ground is important. Tomato plants that sprawl don't produce as much fruit as trellised plants and the fruit is more prone to cracking, insect damage, and disease attacks. Plus, trellising tomatoes will save you space. Unless you're growing dwarf or strongly determinate varieties, indeterminate tomatoes plants can get big and unruly. (Indeterminate varieties keep growing and producing fruits until frost, insects, or diseases kill the plants. Determinate varieties grow and produce fruit up to a certain height, usually about 4 to 5 feet tall. Dwarf varieties grow only a few feet tall and need little trellising). Trellising the large plants keeps them in bounds, allowing you to grow more vegetables, flowers, and herbs in your garden.
How to keep the plants upright is a matter of preference. When I was growing up, my Italian grandfather would stake individual tomato plants, tie the stems to the stake, and prune off much of the excess foliage. This technique allowed him to plant tomatoes closer together, but it reduced the overall production per plant. It was his way, brought from the old country, and he swore by it. This staking method is best used on dwarf or strongly determinate varieties. Pick off any suckers and secure the tomato stems to the stake with loosely fasten twine, cloth, or tomato ties.
Most home gardeners use a variation of my grandfather's staking technique or use tomato cages. The problem with cages is most people get ones that are too small for the tomato variety they're growing. Tomato cages should be at least 4- to 5-feet tall after being secured to the ground. These will accommodate most determinate and indeterminate varieties.
I suggest building your own wire cages made from 6-inch mesh, heavy gauge concrete reinforcing wire bought at a home center or construction supply store. Make sure the holes in the cage are large enough for you to stick your hand through to harvest fruits. Anchor the cages with metal pegs or stakes to the ground. I've even driven a metal or wooden stake down the center of cages to add extra support for very large growing tomato varieties. I like to create cages that stand 5- to 6-feet tall to support even the largest growing varieties.
If you have some of those smaller cages already, don't throw them away. They make great supports for tall peppers and eggplants. These vegetables can blow over during summer storms, especially if laden with fruit, and they also benefit from keeping the fruits from hanging off the ground.
You can experiment with any number of tomato trellising techniques. Consider using wire fencing angled over your tomato bed with room for tomato plants to grow through it.
The old fashioned staking method works best on determinate and dwarf plants. You will have to prune out excessive foliage and tie the tomato stems to the stake to keep them upright.
This tomato trellis method features tomato quadripod tepees joined together with horizontal bars. Using 7-foot long bamboo, wooden, or metal stakes, create a 4-legged tepee at either end of your tomato bed or spaced about 6 feet apart along longer beds. Fasten the top of the tepee with string and secure a horizontal stake to the tepee about 6 feet above the ground between the quadripods. This will increase the stability of the structure and you won’t have to drive the quadripod stakes as deeply into the ground. Attach string along the horizontal bar down to individual tomato plants and tie it loosely to the stems. You may need to use multiple strings per plant for large, suckering varieties.
This is a similar technique used by commercial hoop house tomato growers. Basically you have a structure above the plants and run twine down from the structure attached to the tomatoes. So instead of a quadripod, you can create a structure placed over the tomato bed made from PVC pipe, metal or wood. It all depends on your skill and desire to create garden structures.
This is a tomato trellising method used by commercial growers. It's a great way of creating a hedge of tomatoes. Set wooden or metal stakes so they are 5- to 6-feet tall down the center of your tomato bed. Space the stakes 4 feet apart. When plants are 10-inches tall, secure baling twine or strong string to the end stake and run it down the row wrapping it once around each stake. Weave the string to one side and them the other of the stakes and plants. When you reach the end of the row, weave the string back the opposite way. Do this every week or so whenever the tomatoes are in danger of toppling. It should create a woven mat of string that holds up the plants.
Instead of using wire cages, create a quonset hut from 6-inch mesh, concrete reinforcing wire. Buy a roll at a construction supply store and cut it into 6-foot sections. Bend the wire to create an arch about 18 inches tall. Secure the ends to the ground with pegs or tent stakes. As the tomatoes grow through the mesh wire they will "sit" on top of the arch making for easy harvesting. Large, indeterminate varieties may need a taller arch, so consider cutting some longer wire sections to create taller arches. Fall cleanup is easy. Just lift the cages and tomatoes right out of the ground.