Liquiteq

Pagerank is a funny old thing. High pagerank brings the benefit of a high frequency of crawling, but if the external links aren't of high quality and relevancy, it won't bring any kind of magic rankings on it's own. A good indication of this is a site that doesn't display any backlinks in Google, dispite it's moderately healthy pagerank.

It really doesn't take hundreds of links to acheive rankings, it simply takes a few good ones. A well targeted PR2 site can outrank a lesser PR5 site on the basis of link quality alone, trust me, I do it on a daily basis.

Ouch, you need to ensure that you have some quality content on this page. Most inbound links will be indicating that this is the most important page on your site, and you need to treat it that way. This page should be informative, of a healthy size (in terms of indexable content), and give a clear impression of what your site is about.

Yes. What we are talking about here is called Semantic structuring. Semantics are absolutely vital to illustrating the relevance between categories, topics, and pages. They ofcourse influence your internal link schema at the same time.

This needs to be done "tastefully", as I always say. Logic is the key here. Hierarchical structuring can be well explained by the theory of taxonomy.

http://en.wikipedia.org/wiki/Taxonomy

*Be careful not to stuff keywords
*Use hyphens ( - ) not underscores ( _ ) to conjoin words.
*Try to be efficient, and keep as close to root as you can (where possible)
*Ideally, each parent dir should link to it's child dirs - this isn't always possible.

If this is a script that you're using, you will need to create url aliases for each part of the query string.