Dan's answer is technically correct in every way but I want to remind you why there's no direct way to "follow" somebody on the site. When you follow people instead of topics, your votes start to become targeted. It gives your friends an unfair advantage over others just because of who they are, not on the merits of their posts' quality.
I've covered this in more detail before: Guidelines when voting for friends
If you are going to follow somebody via their RSS, I would suggest you either prevent yourself from voting, or at least make extra-sure that your votes are warranted, and that you're using the rest of the site normally too. If your account registers a lot of votes for one account, it will raise alarms and may even elicit the fabled rusty spoon.
