If you buy a transplant, note the cultivar and then check the seed rack or a seed catalog for information about that cultivar. First, it affects the timing of the harvest. Second, it determines how I will raise the plant. Planting I have seen others fail prodigiously. My guess is that they planted in the morning instead of the evening, and the plants could not sustain the shock in the hot sun.
Plant tomatoes deeply.
Protect from cutworms. Keep pH between 6.5 and 7.0 to prevent blossom-end rot. Anything smaller will just make more work for you. Either way, you must train each vine and pinch the suckers to direct its energy up one central stem. The suckers are the little sprouts that grow from the notches between the side stems and the main vine.