The most common business card size is 84 mm by 55 mm, or 3.5 inches by 2 inches. You can go bigger, but if you do your cards are less likely to be kept. If you go smaller, you have a better shot, as long as they still fit in a typical card folio. Any non-traditional size is going to cost you more money.
For many businesses, one of the biggest challenges of designing business cards is coming up with something truly original. Fortunately, there are plenty of great ways to break away from the norm and create something truly striking. Special treatments are like shiny objects (sometimes literally): they can be very exciting and appealing. But do not let your original excitement make you go overboard. Choosing one two unique elements will let you stand out without being gaudy.
A business card is a physical object that a potential prospect leaves the encounter with. Your brand stays with them. If you meet a prospect and exchange email addresses and phone numbers you each walk away with another contact on your mobile phone -- it ends there. If you hand over a creative business card that makes a great impression that person is likely to show it to other people -- putting you and your brand in front of additional prospects.
When you meet someone that could potentially be a great prospect or connection, do not you want him or her to walk away with a great first impression? A memorable business card does a lot more than just pass on an email address or phone number.