In the greenhouse, potting soil with vermiculite on top. Once they get big enough and the weather is good, I move them outside into the garden.

Lots of compost in the soil with a layer of hay over the top of the garden to conserve moisture (southern CA gets hot and dry).

I'm not clear if you are talking about starting from seed, or putting plants out in the garden.

My seeds are started in the basement using a Seed Starter Potting Mix, and no soil.

When the tomatoes are ready for transplanting in the garden, I add compost in the hole and a compost layer on top. If I have small fish or parts available (usually bluegill), they go about 12 inches down, with some dry compost on directly on top and on the bottom. The plants seem to do better in years when fish are available; although it may be wishful thinking.

I start tomato plants in milk jugs left out on my back deck. Only had to bring in jugs 2 nights since sowing March 3. Now that I think about it the jugs did experience a night of freezing temps and I lost a seedling or two in a couple of the jugs but the stronger, healthier plants didn't miss a beat.

I just potted up the seedlings into 16 oz solo cups this past weekend. Now the cups are in a plastic storage bin that I had hubby put drainage and vent holes.

Our weather has been chilly(lows in the low 40s/high 30s at night), wet and dreary but the plants look great.

If you are talking about growing from seed then there is a great FAQ over on the Growing Tomatoes forum with step-by-step directions and photos on how to do it.

If you are talking about planting them in the garden then check out the post linked below. It is a classic and frequently referenced on the Tomato forum.

Dave

Here is a link that might be useful: Earl's hole method...

yeah, i just realized that, i meant how do you plant them...i already bought them a few inches tall.

This is a good example of nomenclature causing confusion. I notice that many contributors refer to 'planting' seeds. This is fine if there is further info. on what is meant but can lead to lack of clarity. It would be clearer if we tried to differentiate between sowing and planting on these forums.

I make sure the soil they will be planted in is well endowed with organic matter so it will be evenly moist but well drained and evenly balanced with nutrients with a soil pH between 6.2 and 6.8 from a periodic good, reliable soil test. That has allowed me to grow good tomatoes that are disease and insect pest free that do not get Blossom End Rot, cracking, Cats Paw, or other cultivation related problems.
Starting them inside from seed is done in compost.

yeah, i just realized that, i meant how do you plant them...i already bought them a few inches tall.

If the plant is leggy, I plant them so only the top 2 or 3" is above the top of the soil. The buried stem produces roots all along it. Some people remove the leaves that will be buried, and some don't. I don't.

If the plant is lush and looks happy, I just plant it.