When I receive a comment from someone, or see them in the forums or the answer sections, sometimes I go to their profile.
If I see that they have a lot of hubs that might be of interest to me, I follow them. When following, there is an option to send fan mail right away. Since it will show up on their profile anyway, I will post fan mail, mostly to say hello and tell them they have interesting topics. The fan mail is not to tell them they are wonderful - just to let them know why I want to follow them. It is too hard to remember later to send a fan mail, so I do it up front. It seems stalkish to follow someone without telling them who you are, or why you want to follow them.
Then I go on to read their hubs. Sometimes I comment on hubs, sometimes I don't, depending on how busy I am, and depends on if I can think of something to say about the hub.