First, choose the right light. Second, have enough light. The most common mistake of most gardeners is to have too little light. A simple rule of thumb is you need 40 watts of fixture per square foot of growing area to grow most plants.
Third, keep the lights the right distance from the plants. Fluorescent lights need to be 1 to 4 inches from the plants. HID lights should be 1 to 3 ft. Finally, change your bulbs on a regular basis. Fluorescent and HID bulbs will last 15,000 or more hours but they lose 25%to 35% of their intensity after 4000 to 6000 hours of use. Your eyes do not often see this loss of light because they adjust, but your plants can feel it.
When choosing a light source the requirements of the plant you are growing is important. Most vegetables, herbs, and flowering plants require high levels of light, while some tropical plants including orchids and African violets will thrive at lower light levels. Probably the biggest mistake made when purchasing a light is not getting enough light. It is always possible to reduce the level of light by moving the light farther away but i is not possible to add light by moving the lamp closer as you will lose coverage.
Gardening indoors year-round can be fun and rewarding. One added benefit is that weeds are rarely a problem and insects are more easily controlled. With the right light, you will be surprised at how effortlessly your plants grow.