Tomato plants have a reputation for being difficult to grow inside. The trick to growing tomato plants indoors lies in choosing appropriate varieties. While you may not have much luck growing large slicing tomatoes indoors, petite varieties can yield bountiful and delicious crops without ever leaving the comfort of home. Adequate light, fertilizer and watering are the only other important elements in the tasty indoor tomato equation. Hydroponic or aeroponic solutions exist as well, but are much more expensive and not really necessary to grow tomatoes inside.
Choose appropriate tomato seeds for indoor growing. Robert Cox of Colorado State University's Cooperative Horticulture Extension advises petite varieties such as Tiny Tim, Small Fry, Pixie, Patio or Toy Boy. Larger tomato plants will not fare well in such confined spaces as 6-inch windowsill pots.
Plant your tomato seeds in starter mix in a flat. Water them lightly and place them in a sunny window, preferably south-facing. If you do not have a south-facing window available, east or west windows are your next best option. Whichever window you choose, make sure the sun is not blocked by buildings or trees.
Observe your tomato seedlings as they begin to grow. Once they have reached a few inches in height and look healthy, transplant them to potting-soil-filled pots. Fill the pots with potting soil first, leaving a hole that is longer than the depth of each tomato plant's root ball. Carefully loosen the plants from the flat by squeezing the flat's sides. Try not to tear the roots or expose them to air and light for a long period of time.
Water your tomato plants whenever the soil feels dry. Make sure the pot has good drainage. Fertilize with tomato fertilizer according to the package instructions.
Stake your tomato plants as needed with lengths of 1/4-inch wooden dowels. You can obtain these from home improvement, garden or craft stores.
Shake your tomato plants lightly once they have begun to flower. Since you are growing them indoors, your tomatoes will not be fertilized by bees like they would outdoors. Shaking them helps to distribute the pollen, and should yield you some beautiful baby tomatoes soon afterward.