There needs to be some sort of incentive for them to come back. Something about your site needs to keep them hooked. Its really different for every case, but t

There needs to be some sort of incentive for them to come back. Something about your site needs to keep them hooked. Its really different for every case, but take fb for example. You want to see what your friends are posting. You need new information that they wont see unless they go back to your site.