1. Dirt wrap - you know how some spas offer to surround you up to your chin in warm, clean, mud? Well, that's exactly how tomatoes like to be planted. I personally believe that is why they have such cute, hairy stems. Those hairs are actually potential roots, ready to develop and suck up nutrients.
Just trim off the lower leaves, nestle the plant in up to its leafy chin and give it a great, big initial drink for its summer heat treatment.
2. Feed me - tomatoes need to be fed about once a month after planting. There are many and complicated recipes. However, a balanced organic fertilizer that emphasizes phosphorus is a good choice, e.g., a 4-6-4. Phosphorus, the second number in all fertilizer forumulas, is key for fruit production. Many good organic fertilizers can be purchased at your local nursery. We got our plants off to their great start with combinations of products from Dr. Earth, Whitney Farms (currently, a Scotts company), and E.B. Stone.
3. I'll have another sip - be consistent in watering tomatoes after planting to avoid "bingeing". It's not good to drown them one day and follow up with a week of neglect. You can easily monitor the plants' needs by sticking your finger down a couple of inches into the soil. If it's dry, they may need a drink, but maybe not: tomatoes like a bit of drying, even to the point of mild wilting. Mulch also helps -- it slows down moisture loss and keeps roots cooler by providing shade for the soil. Put the mulch up to about 6 inches from the stem; that way, certain pests won't be able to stage a sneak attack under the cover of the mulch.
One last thing: rotate your tomato sites year over year for disease control. Many of the most common tomato pests live in the soil, but you can usually outrun 'em by planting in different locations.