Hand out your business card to anyone who may need to contact you.
Give those close to you, business wise or personally a few business cards so they can hand them out when they meet someone in need of your product.
Always have your business cards with you.
Place a special offer or product information on the back of your business cards.
Give a client a few extra business cards with their name written on the back. Offer to give your client something free if they give the card to a friend and the friend brings the card in. You could offer a special discount to their friend also.