You could also offer invitations to events, promotions and discounts to your audience. For best results, use this method as an enhancement to mailing list your to social media marketing or search engine marketing (paid advertisements such as pay-per-click, cost-per-click, cost-per-lead, cost-per-action, solo or banner advertisements).
You can also include in all your advertising tactics, a personalized barcode which links to your mailing list. Be sure however, to set up an mailing list auto-responder to manage your sources of leads in a futuristic way. There are free or paid ones. Mailchimp is a favorite of mine. You could also use InfusionSoft, Silverpop, Constant Contact, Aweber and a host of others. When all these methods are done well and in combination with well thought out keywords for SEO.
Your subscribes will love and follow you to the ends of the earth. Are you searching for more traffic in all the wrong places? Try creating free reports for your products and affiliate offers. Even if you do not make a sale they may opt-in which will mailing list help build your mailing list. Sometimes people that visit your web site for the free report are just looking for ideas.