i think you can build some sites which people like, after some time when they have pr4 or more, then you can get 3 way links.
If you have good content then try to contact other webmasters in your niche and ask for a link. Tell them why your site would be valuable to their visitors. If your site is a very tight niche then contact webmasters who have several topics related to your niche (your site would be a sub niche of theirs). If you have a very general topic site, then contact websites that target a sub niche of your site (their site would be a sub niche of yours).
If you have Back links from social sites within content and relevant to your theme, it can effect your site's ranking. PR and less outgoing links also should be there.