When designing a business card, the main thing to remember is "what is the point"? The purpose of a business card is primarily to provide someone with your contact information. Chiefly your name, title, phone number, email, address and website.
Many times we see examples of business cards that people are treating like flyers, cramming as much information as space will allow. (ex. 10% off! Punch this card 5 times and get one free! By the way, let me tell you a little about myself. I was born in blablablablabla... etc.) This is not a good idea. It leaves an impression of confusion and disorganization, which are not words that you want your customers to associate with your business.
If your main goal is to advertise, it's best to stick to flyers, postcards and marketing brochures. These items are larger and built for colorful graphics and ad copy.