Basements can often be added space to your homes use. If it is pretty much finished, you don't need to do alot to make it a livable space. Most techniques are often simple and inexpensive.
Getting rid of the Moisture should be your first step. Then you will check for any leaking pipes, and windows that are not sealed. Or look for any other water source that may be getting into the basement. Doing this will prevent any future problems, or health issues. You may want to use a dehumidifier in your basement. A dehumidifier will help avoid mold problems.
The color of your basement is also a key ingredient, color makes it visually interesting and will make it functional. The color will go with the purpose of the basement. Small basements do well with light tones, or pastels. For a modern look, use jewel tones or dark rich tones. Brown or navy will prevent glares if your basement is used for a entertainment area.
Flooring in your basement is also important. Ceramic tile will resistant any moisture or warping. A are rug will keep the room comfortable year round, and add texture. At times some hardwoods can be used.
Your lighting is as important as your color. It will need to be functional for your basement. You can have natural light or light fixtures. Overhead track lighting is often used as a option. Often dimmers are added to the lights for balance.