When someone likes your page, they can immediately be subscribed to receive updates. You should also have an 'email subscribes' box on your Facebook profile so people can subscribe directly from that area.
4. Get people to promote your business online. If you have customers who are willing to share your website with their friends, it will be easy to have people join your mailing list.
6. Referral programs. If you have a site like ebay.com or craigslist.com, where you are selling items, offer your customers a reward for referring their friends to your online store or business.