Facebook and Twitter are great channels that marketers can use to reach new audiences and participate in two-way interactions with consumers. Unfortunately, both social networks are also undeniably scattershot as marketing tools. Segmenting and personalizing your communications effectively using either one is difficult, and even your most dedicated fans and followers will likely not read many of your messages.

The chronological layout of Twitter timelines, coupled with the sheer volume of tweets many users receive, makes it almost inevitable that your followers will miss some of your tweets. And Facebook's EdgeRank algorithm can prevent your posts from appearing in your fans' News Feeds if you're not creating content that's consistently interesting to them.

Those facts make a good case for the need to write compelling social media content. They also underscore the value of converting your social media followers into SMS- and email-marketing subscribers. As people who have a genuine, expressed interest in your products and services, your fans and followers are the perfect targets for those efforts.

By recruiting your social fans and followers to your email and SMS lists, you can forge deeper relationships with them by offering more personalized and targeted content than you ever could via social media alone.

You can also increase the likelihood that your communications will be read—particularly in the case of SMS, since 83% of all text messages are read within an hour of being received.

Here are five steps to accelerating your email and SMS list subscriptions using social media.

1. Attract more fans and followers

Publicize your presence on Facebook and Twitter in your stores, on your website, and in your ads. Facebook ads are another cost-effective way to get more fans. Entice people to "fan" or "follow" you by offering them exclusive content they won't find anywhere else, and emphasize giveaways and discounts.

One study found that 37% of Facebook users "Like" fan pages just to receive coupons and deals. "Liking" (Facebook) or following (Twitter) you is a lighter commitment for customers than opting in to your SMS or mobile lists. By acquiring social followers and offering them relevant deals, you can help them see the value in joining your lists.

2. Convert fans and followers into subscribers with a web form

Dedicate a permanent tab on your Facebook account to a Web form that people can complete to join your email or SMS lists, and tweet a link to your form on Twitter. To grow your lists quickly, offer incentives for filling out the form. For instance, Signal customer Culver's, a Midwestern fast-food chain, offers its new subscribers a free value meal for joining its eClub and a free scoop of frozen custard for joining its Text Club on Facebook.

3. Ask people to text for a coupon or offer

Invite your Facebook fans or Twitter followers to text for a special offer. In return, ask that they join your SMS or email list, while emphasizing their ability to unsubscribe at any time. Movie and game rental company Redbox (also a Signal client) has had success doing that by offering customers a free rental in return for joining its email list.

4. Run a sweepstakes or other social promotion

Sweepstakes, voting contests, and trivia campaigns engage followers, and they also allow you to add them to your email or SMS lists as the price of entry. Signal customer Memphis Car Audio recently ran a social sweepstakes tied to email-subscriber collection. By offering a trip for two to the Brazil premiere of the movie "Fast Five," the company successfully increased brand awareness, drove in-store traffic, and added more than 93,000 subscribers to its email list.

5. Reach new audiences using referral bonuses

Rewards for referrals—a common tactic used by your favorite daily deals sites—can be a powerful tool for accelerating list growth beyond your current fans and followers.

Ask all new subscribers—right on the confirmation page they get after signing up using your Web form—to refer their friends to also join. Give each referred friend an offer or coupon for joining, and give the referrer a special offer of even greater value if she refers a specified number of friends.

By attracting your social fans and followers to your subscriber lists, you can develop a universal profile of your best customers across all digital channels. Over time, by analyzing your fans' and followers' responses to different communications, you will be able to determine the type of deals each prefers and whether they respond more favorably to an afternoon tweet, an early-morning email, or a midday text.

Ultimately, that information will enable you to create the kind of highly personalized offers that inspire customer loyalty and repeat business.