Anyone who is building a Web-based community, whether it be a social network or other application, faces the same initial hurdle as sites such as Digg did: getting those first few regular users can be quite difficult.If you're lucky, you won't have to spend money buying banner ads or search-engine keywords, as was the case with Digg. The social news site's rapid rise made it one of the Web's early success stories, but there's quite a few things needed to keep people engaged, said Kevin Rose, the site's founder.Rose spoke to Web developers and marketers at the Future of Web Apps conference on Thursday morning before Mike McDerment, the CEO and co-founder of FreshBooks, an online invoicing application. Both addressed ways for how Web developers can attract and retain new users, which is the most important metric by which an application will be judged.The microblogging service Twitter struck Web 2.0 gold with its concept of becoming a "follower." Users want to gain more followers, and many don't even care if many of those followers are spammers, Rose said. Twitter has also benefited from the high uptake by celebrities, which amounts to attractive free promotion."Love it or hate it, it has fueled Twitter's growth," Rose said. Digg has incorporated several features to reward its users. For a while, it had a leaderboard, which showed how many stories a person had posted, and many people vied for the top spots. Digg is revamping the leaderboard to make it easier to make the list."Everyone wants to see their name in the light," Rose said.Another key tip when designing a Web application is to not make it too feature-heavy, as users are probably only going to use between 20 to 30 percent of the features anyway. Developers should also avoid "analysis paralysis," instead adopting a schedule of building, releasing and then repeating the cycle, Rose said.Digg has also been savvy about teasing the media. Digg distributed a few special invites to test a new version to bloggers and a few media, which built a bit of suspense for the release, a technique Rose termed "hack the press." In one instance, Digg's approach landed a story in The New York Times. But even junior bloggers should not be ignored, as they're more likely to pick up a story than perhaps much larger media organizations.McDerment's FreshBooks service started from humble beginnings, with him slaving away on it in his parents' basement for more than two years. FreshBooks now has more than 1 million users, in part due to careful analysis of traffic.FreshBooks offers a free service with the ability to invoice three clients as well as expanded options that rise in price. The "freemium" version -- a tactic used by many other Web services -- is a good hook into eventually converting people into paying customers, McDerment said."If they're started using it, they're going to buy it because it's awesome," he said.But figuring how the cycle of who will turn into a paying customer and when is important, and that's where analytics comes in. McDerment said Web developers need to know where people who end up on their site last came from, where they landed on the site and what keywords are important.That helps figure out where best to spend marketing funds in order to get the high-quality traffic that eventually turns the freebies users into paying ones."You can be misled so easily by poor data," McDerment said. "The fog of night is lifted when you have hard data."