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Heavily cross linking will lead to a flat distribution of PR, i.e. all pages of your site will get nearly the same PR. This is a good strategy, if you have numerous important pages (e.g. different product pages). On the other hand, if you are optimizing just for a single page, a hierarchical structure without cross linking would be the better way.
Following the advice that Google puts out of no more than 100 links/page, you would be forced into a hierarchy at this level as it is. But that's a good thing.
Using a pagerank calculator allows you to look at the internal linking structure of a website and determine the relationships between internal links.
I got a lot out of using one of these, as I was able to understand how the internal linking can influence my own internal pagerank.