In the days before such a myriad of electronic communication was so readily available it was the common practice of the gentry to use "calling cards". The practice originated in Europe in the 17th century as an absolutely crucial staple in the etiquette of the aristocracy.
Named for the practice of "calling" on one's friends and family, calling cards, according to etiquette, were to be left in a tray near the door or with a servant of the potential host. This practice was used both for decorous introductions as well as before regular visits. If the host was willing to entertain the caller, he would send a card of his own. On the contrary, if a gentleman did not wish to accept a visit, he would either not send his own card in response or else he would send his card in an envelope. The card within the envelope was, in effect, a blunt but well-mannered refusal. Likewise, a card sent within an envelope following a visit will signify that no such visit is anticipated again in future (often as a result of a bad visit).
A gentleman's calling card should be simple. It is generally the same size as a modern business card. A gentleman's name should be written in the centre in elegant, but tasteful font. Include little additional information, though some contact information may be included for convenience in the modern day. We also recommend including a personal or family motto, preferably in Latin, though French will suffice. The back should be left blank to leave room for personal notes and the like.
Today there is still a use for calling cards, despite the noticable absence of servants to deliver them. Apart from being used in the traditional fashion or as a means for exchanging information, calling cards can be used as invitations, to respond to invitations, or to exchange greetings. This can all be done by penning messages onto the back of the card, or the blank portion of the front, if it fits. For instance, "Lord Wilburforce, please drop in tomorrow afternoon for tea at four o'clock. R.S.V.P." can be scrawled upon a card, to be delivered or slid under an office door.
There are other means of conveying messages using calling cards as well. The turning down of different corners of the card have varying significances, as below:
Upper Left - A congratulatory visit is sought.
Upper Right - A visit in person, usually immediately as the card's owner is already present, is requested (in lieu of the card having been delivered by a servant).
Lower Right - A visit before taking leave is sought.
Lower Left - A condolence visit is sought.
Additionally, similar messages can be conveyed using various initials, usually from French expressions, viz R.S.V.P.:
p. c. - For condolence (pour condoléance)
p. f. - For congratulations (pour féliciter)
p. f. N. A. - New Year's greetings (pour féliciter Nouvel An)
p. p. - To request a formal introduction (pour présenter)
p. p. c. - To take leave (pour prendre congé)
p. r. - To express thanks (pour remercier)
More on the Calling Card:
Victorian Calling Card Etiquette
Gentleman's Guide to the Calling Card
How to Use Your Calling Card