Currently I am doing comments, hoping to bring more backlinks. Should I comment more on do-follow forms? Expect for some suggestion. Thank you first.
Isn't that obvious? If you are looking for link juice(for SEO) go for do-follow blogs. If you are looking for traffic do it all.
Google counts only the dofollow links but Yahoo! and MSN counts nofollow links too. Do it regardless of nofollow or dofollow when you are building links. after all you want to do SEM!!!