How can I be informed about or follow other users’ new submissions, comments etc.?

In order to follow another community members, and thus keep track of his/her new ideas, comments etc., just move the cursor over their profile icon and click the “+” sign. You then "follow" this person, and get updates on his/her activities on your dashboard.

You can also "follow" a project to keep track of the ltest submissions, updates and comments on the briefing.

More on the 'follow' feature in this blog post.