In my opinion there are few things as important as building good quality links to your website.  The search engines count each link as a vote when deciding which sites to show in the search results.  A lot of links are good, but links for authority sites are better.  The links from non-authority sites help a little as long as they aren’t from bad neighborhoods.  Personally, I don’t have the time or the desire to try to figure everything out so I sue a professional link building service to do it for me.  They do a great job and produce real results.