Don't over-fertilise tomatoes! Here's a good feeding schedule
My tip for growing tomatoes is to use a good fertilisation plan.
First, use a good, balanced fertiliser during pre-planting, working it into the soil just as you would for planting potatoes.
Then, I don't apply any more fertiliser until tomatoes begin to ripen. At that point, I use a little 0-5-5 - no nitrogen - once only. This is where I believe it's easy to make a mistake. By fertilising too often, tomatoes get too much nitrogen, hence too much top leaf growth.
One more thing: gypsum is a great soil conditioner for tomatoes. It contains calcium and sulphur which keeps your growing medium from packing down.Tomato Dirt footnote:
Great points from Allan! You may want to consider two of the most respected tomato fertilizers out there for your second application: Tomato-tone Organic Fertilizer
and Miracle-Gro Tomato Plant Food