Internal Link Structure - Do this right!
Starting off with a good internal linking structure is important. You need to be able to pass as much Page Rank back to your main page as possible.
If you will notice that at the bottom of this page there is a link pointing back to the index, that's so each page in the site SHOVES PR back towards the index page. Each page here has a value and all of them are pointing some PR back towards where they are linking. If I had 40 links on this page, it would be about worthless as a PR pushing page.
However very shortly after google updates, the index page will have a decent PR from the links from articles, back links, and internal links I have on the site.
There really is no way to not do proper internal linking with out planning ahead so do it in your SEO planning stages.