You have the option of planting Tomatoes with or without Cages. Cages have been shown to be a plus. They minimize plant sprawl, elevate the Tomatoes above the Insects and Rodents, keep the Tomatoes cleaner, minimize rot, allow them to ripen more uniformly, and raise them nearer eye level.

Minimizing Sprawl means you have more free space to plant more Tomatoes or other vegetables, or prepare less garden for the same amount of plants. Either is a plus.

Elevating the crop above the soil may be the greatest advantage. There is less chance of missing some Tomatoes because they are not hidden in the foliage. And all the ground-dwelling pests will go hungry.

You can use store-bought Cages or make much better ones with a little labor. First go to your local Building Warehouse and buy some Concrete-reinforcing wire mesh.  If they sell only full rolls, try a local Concrete Contractor. This mesh is made five feet wide with six-inch mesh. That will make a cage 5 feet high and allow your arm to reach inside the cage for weeding and harvesting.

The Cage can also support other crops (Pole Beans, Watermelons and Cantaloupes love to climb these Cages), so don't be stingy with the size. 3 feet wide by 8 feet long makes a good Cage for the Garden. That will require a piece of mesh 22 feet long. allow an extra 6 inches for overlap.

Start by measuring 4' from one end. Bend the mesh at 90 degrees at this point. Then measure 3' and make another similar bend. Measure 8' and make the third bend. Measure 3' and make the last bend. This will put the seam in the middle of one 8' side. The seam can be secured with optional wire, or hooks created in the overlapped ends.
A storm can blow this Cage over if the plants are young and fail to anchor it adequately. 2 Stakes at opposite corners will minimize this tendency. A 3/8"round Post that is 3 feet long and has an "arrow" on the bottom works great for this purpose. It is pounded in the soil at an outside corner with the arrow on the top. This allows the arrow to hold the Cage down as shown in the photo above. Pound it into the soil at least a foot. A piece of optional wire will hold the Cage to the Post.

In use, Plants can be put inside and outside the Cage. Optional smaller-mesh fencing put inside the Cage will also prevent Rabbits, etc from dining on your Plants. Tomatoes may have to be woven into the mesh as they grow. Climbing Plants like Pole Beans need no help from the Gardener.
Most Vegetable Plants should be planted at the same depth they were in the pot. Tomatoes are a notable exception. They will develop roots anywhere along the stem where it touches the soil. So you have the option of removing some of the lower leaves and burying the main stem in a horizontal trench. Or you can plant them in a deeper hole.

Either method will develop more roots to extract more nutrients from the soil and develop larger plants which grow more Tomatoes and can better withstand dry conditions. So it may be beneficial to take advantage of this characteristic.

Loosen the soil with a Shovel or Tiller. Then create a hole at least twice as wide and deep as the Root Ball. Put Compost or amended Soil mixed with manure in the bottom of the hole. Set the Plant on this enriched soil and add more around the Root Ball. Firm it in with your shoe or fist. There should be no air pockets to allow the Roots to dry out.

Then water the plant and add regular soil to ground level. A saucer effect may be created to hold water. Enriched soil should not be put on top of the Root Ball as this will encourage roots to grow near the surface where moisture is minimal. It will also encourage every known weed to grow there. It is best to use soil near the surface, which is not very rich in nutrients.