Yeah one should update fresh,unique and useful content at regular basis.But one should go for some link building techniques too.In addition to your techniques article submission and bookmarking, i have considered guest blogging,forum commenting,directory submission,Press release,video submission as my link building techniques.

Well as many above me said i would have to name the content as the most important factor when it comes to page ranking!

Thanks for sharing.

Search engine ranking is determined by a algorithm in which uniqueness of content is only one minor score in the overall picture. The main ones are keyword density or relevance and link neighborhoods (backlinks) and lastly age which plays a major roll. So it's most important to have relevant content, with sites that are related back linking to it that are aged as much as your site if not more.

Yes fresh content is very important.

Content is the king.