Internal links dont cost anything. They can be targeted, from within relevant text, to relevant pages, making them stronger and more valid. You can increase the PageRank of a page with internal links. You homepage usually has the highest PageRank of your site, so create an internal link from your homepage to the page that you want to pass the PageRank on to (ie a page where you’re optimising a competitive keyword that doesnt fit on the homepage). Use descriptive anchor text. Use the keywords that the linked-to page is about, this will help the search engines and your users to know what the link goes to. You can use this technique to help your internal pages attain higher rankings