Yes, comment and correct like crazy! Even if a question or notebook had answers, I still would comment and give my two cents or even just give a "welcome to italki!" comment. That's how I found all my students at the beginning. Also want to make your availability as open as possible at first, then you can cut down later if need be.

When I started on this site last year, I think it helped to answer student questions under the "Answers" tab and to correct "Notebook" entries. This gives you greater visibility.