Planting tomatoes for the first time? Maybe been growing them for a while, but just been putting them into the ground without much thought to their roots? If so, did you know that tomatoes like to be planted nice and deep? Tomatoes are one of the plants that thrives on being transplanted because they love it when you bury their stem deep. I do this when I transplant the tomatoes from the seedling cells to the 4" pots and again when I plant them in my garden. This helps build a strong root system, which means better access to the water and nutrients in your soil.
All those little hairs and bumps that you see on a tomato plant can become roots if they get close to or touch the dirt. This is why sometimes when you buy a tomato plant you'll see roots right at the surface. This isn't a problem plant, it's one that is developing a better root system.
Plant part of the stem
When you dig your hole for your tomato plant, be sure to dig it quite a bit deeper than you'd need just to sit the plant down into the dirt. This is because you're going to plant at least a couple inches of the stem into the dirt as well. Carefully snap off any branches that are on the part of the stem that will be planted, as well as those within a few inches of the ground. Once the plant is tall enough, I snap off any branches that are within a minimum of 6" of the ground since those leaves will end up splashed with water and can end up with fungus and other such problems.
I also throw a handful of long lasting granular fertilizer in the hole before I plant the tomato start. This is especially important if you're container gardening, like I am. Then I plant the start.
By doing this, you give the plant the chance to build an even better root system, which means more tomatoes and a healthier plant.
Pinching off flower buds
I know it seems crazy, but you will want to pinch off any flower buds that pop up while your plant is still small. This is because you want your plant putting all of its energy into growing the plant and not growing tomatoes yet. This means you sacrifice some tomatoes at the beginning, but are helping to ensure a lot more tomatoes later.
If you let tomatoes grow on your plant while it is still small, your plant won't get as big as it can. That means it won't be able to produce as many tomatoes, will be more likely to break if you have larger tomatoes, etc.
Once the plant is a good size (4'+ with a good amount of healthy branches), then I allow it to grow buds and produce tomatoes.