Is there any such thing called internal links (links to other pages on the same website) and external links ratio w.r.t. SEO? I'm aware that about 20-25 outgoing links from one page can be considered as a norm but I'm not sure of the internal links and its affect on SEO/PR etc.
What I know is that besides getting links from other sites it is also good to have a good linksystem for the inlinks. If you link to another page you vote for that page with what you have. So there will flow value from you site to the other but it is so minim that you shouldn't worry about that. Just be generous with your links and hope that others will also be generous to you by linking back. By linking to a certain page on your site very much, you also give a sign to google that the page is more valuable than another with less links from your site to that page on your site. But about the ratio I don't know, it is a very complex calculation. To know how your pagerank might be calculated look here: webworkshop.net/pagerank.html