Facebook’s Sheryl Sandberg offered up some tips on how businesses can best use the social networking site during Fortune’s Most Powerful Women Summit.

The biggest key: companies can’t think about using the site in the same way they have conceived of traditional advertising, says the Facebook COO, who is No. 22 on Fortune‘s 2009 Most Powerful Women list.

The beauty of Facebook is the immediacy with which businesses can reach their consumers. A traditional advertising campaign might take six months to roll out, but Facebook erases that delay. Companies need to leverage that, she says, so it’ s better for companies to spend half an hour a day on their Facebook strategy than one day a week.

“This isn’t about perfect messaging,” she said. “Do it often and quickly and imperfectly and just keep changing it.”

Some groups that are using Facebook well, according to Sandberg: President Obama, who, with about 7 million fans, has the largest following on Facebook.

Sandberg mentioned the Huffington Post, which by integrating Facebook has given users a more personal experience. She also pointed to a more traditional media content provider — Disney owned-ABC’s Lost, which has more than a million fans and uses the page to post unique content.

The biggest pointer for using social media she says: “Just do it quickly.”