In a market where workers are scarce, more and more companies are relaxing their dress codes as an inexpensive way to improve employees' lives and productivity.

In 1998, a study by the Association for Applied Interactive Multimedia (AAIM) found that 80 percent of the small businesses have a business casual dress code. About 60 percent of them have a business casual dress code all year.

Even though the requirements for "casual" and "business casual" are different for every company, some general rules apply. Business casual is more formal than casual. Many companies require men to wear long-sleeve shirts, pants, socks and dress shoes.

Sherry Maysonave, the author of "Casual Power: How to Power Up Your Nonverbal Communication and Dress Down for Success," says collared, knit shirts are a must-wear for men. For women, dress code may be a little trickier. Still, dress shoes, long sleeve shirts with pants or skirts are necessary, and blazers are desirable.

On her web site, Maysonave stresses the importance of grooming for both men and women. Women, she says, must wear makeup, but not too much. Either extreme, she says, would send the wrong message: instead of showing high self-esteem, it would reveal not having any at all.

A good rule of thumb: follow the dress code higher executives wear, keeping an eye on your co-workers, to be sure you are not dressing down (or up) too much.