As an author, you should always be prepared to attract new readers. One way to do this is to always have a copy of your book on hand. This is absolutely an excellent technique if you frequent public transportation such as the city bus, subways, taxis, etc. Someone is prone to ask what you’re reading and you can gain a potential reader/fan
Also, have a supply of your business cards to pass out to everyone you encounter. You do have a business card, right?