Use stickers and stamps as well as hand written notes on all mailers and day-to-day business mail. When you put a sticker or handwritten message on the outside of an envelope it has the impact of a miniature billboard. The message should be short and read in less than 10 seconds.
Put your best add on a postcard sized mail piece. Send it to all of your prospective clients. People will read your message if it is brief, even people you did not intend your message for will read your add. Be sure to include your website address so people can get more information if they want to.
Information from About.com