Besides a website, this is the most import bit of marketing material needed to advertise, for some businesses. Business cards can be seen as the non electronic website, if constructed properly. As a designer, you could put your images on there. For example, some photographers have put their photographs on one side and their contact details on the other, and also made them into a size that is a little bit larger than the regular (85×55 mm).
There are different shapes that you can use, to fit your business/the industry you work in. For example, I have seen mechanics use a spanner or a toolbox outline, which is obviously very different to a standard card. But there is nothing wrong with the standard card either, it seems the more traditional route also.
Some advice given in the past have been things such as:
“I leave the back blank for a space to make notes”
“Put all social media on there”
“Don’t give away too much information”
“Create a unique design/layout”
Meeting someone who had advertised 2 businesses on each side of their business card was another show of creativity. But the message of a business card is to represent your brand, so the consistency needs to flow with all materials for your business.
Pt.2 will contain detail design placement examples and printing options.