Your database is the backbone of a successful email-marketing program, and there's no better time to build it up than during the holiday shopping season, when hordes of motivated and interested shoppers are coming to your Web site. This year, more than ever before, your list-growth strategy should include a plan to offer opt-in opportunities to shoppers in every channel where you have a presence. These should be optimized for the advantages as well as the limitations of each channel. Following are five key areas to collect opt-ins:

Emails are getting cluttered. It's not enough to have a headline, some copy, and an image or two anymore. These days we need preheaders, snippets, "view this email online" links, and all sorts of social sharing links as well. Some marketers are starting to question whether we need all of these links when most of them drive very few clicks. And first on the chopping block seems to be those "share with your network" links.

Email offers a number of powerful advantages for marketers: prospects and customers like to interact via email, it's cost effective and it's easy to measure results. Although there are many metrics to use in an email marketing campaign, when measuring email effectiveness you're really trying to answer three questions: