Business cards are a form of our marketing message. They are part of our brand in that they let people know how they can connect with us. Often when we meet someone we have just a brief encounter. Sometimes it only long enough to say hello and exchange cards. Other times it's a much longer meeting or even a sales presentation. There the business card provides a means for the people we have been meeting and speaking with to maintain contact with us - in writing, by phone, email, or text - as they desire.
If we have a storefront or an office where we receive people, the exact physical address (rather than a P.O. box) should be printed on the card. The complete address needs to be there. Whether it's an oversight or we just think people will understand that we are local, many business cards omit vital information such as the name of the town (showing just the street address), the name of the state (apparently thinking this would be assumed by potential receivers of the card), and the zip or postal code. When all of the business is local, it's not as important to have it, but it doesn't cost anything more to include it. We are not paying for our cards by the number of words or letters.
As long as the business cards remain local after they are distributed and the people receiving them remain local - and if the business name or the area where it is located is somewhat known in that area - leaving off the state name and zip code may not be a big deal. However, as soon as someone takes that card from that location and returns to their home or business miles away, or they receive this card at a regional or national event, the recipient of the card can't readily tell where the business is located without going online to do additional research - assuming they are interested enough in contacting this business again.
In a similar way, the telephone number needs to be complete. Many business cards omit the area code or country code (when the business is international). Again, if the clientele is local and people recognize the name of the business, remember where they got the card, and understand that this is a local call, not having the area code may not too much of an issue. Nevertheless, there are many places where ten-digit (the three-digit area code along with the regular seven-digit telephone number) calling is required. In some markets, there are more than one area code that applies. Even when the clientele for the business is local, as soon as someone travels outside their local calling area or area code and tries to call the business, they are not able to do so without dialing all ten numbers.
Legibility - having the type large enough to read without picking up a magnifying glass and having it in a clean easy-to-read type face where similar looking letters or numbers are not easily confused - is important. Sufficient contrast also helps - being able to see the print and have it stand out from the background. Black ink on white cards have been the mainstay of business cards forever. Color adds interest and variety, but the main thing is to have the cards be useful to the person getting them by having the information contained on the cards be easy to read.