A business card may be the most overlooked advertising medium in the business world. But these simple rectangles of cardboard can be powerful tools to help any entrepreneur increase sales. Similarly, a poorly thought out or clumsily designed business card can be as much of a detriment for your sales as an "out of business" sign.

Business cards have actually been around for much longer than most people realize. The first ones, in the form of visiting cards or calling cards, were used in China about 600 years ago. They started being used in Europe approximately 200 years lager. When one aristocrat went out to visit another, the prospective guest's servant would deliver his master's calling card to the servant of the prospective host. An elaborate system of calling card etiquette developed and was followed by the gentry across England and France.

Today, anyone from North America or Europe who has gone on a business trip to Japan, China or other Asian countries knows there is very much a tradition of etiquette that must be followed when exchanging business cards in those countries.

But even if you are only going to be doing business in your home town, you can help boost that business by following four tips before you have your next business cards printed.

1. Legibility. It's fine to have a creative, attractive design for your card, but do not fall for the trap of selecting a type face that is so fancy it is not legible. If people cannot decipher all the words and numbers on your card, it is useless. Also, remember that, especially in this era of aging baby boomers, type that is too small may also be difficult for some old eyes to read properly.

2. Individualize. You are a unique individual, and your business card should reflect your unique personality. One easy way to do this is to put your photograph on your card. Of, if you are an artist, crafts person or photographer, why not put an image of one of your creations on the card? If you sell unique widgets, put an illustration of them on your card.

3. Proofread. Just as a wood worker should always measure twice before he cuts, every word should be double checked for proper spelling. Every telephone number should be dialed and every web address visited to make sure they are letter perfect before your card goes to press.

4. Use the back. Your business card has two sides, and you are missing a prime opportunity if you leave the back of your card blank. Instead, utilize that space to say what is most important about you, your business, product or service. It could be as simple as "bring this card in for a 10% discount." Or you could use the back of your card to show off testimonials from some of your satisfied customers.

There are several very good internet business card companies that let you design your own cards online. In some cases, their shipping costs are less than it would cost you to drive to a local print shop and back.

Finally, if you only need a few cards, or if you want to experiment with different card designs, you can purchase perforated, blank business card stock at office supply stores and make your own cards using templates that come with many computer word processing software programs.

However your business cards are eventually printed, remember that they may leave a lasting impression of you and your business for many years to come.