Nice subject,
Infact Search Engine Optimization is not something easy to do, you need to have links everywhere mainly on websites who have high page rank.
For example if your page rank is 2 and you had a link on a website page rank 5 it will help you to get a better page rank.
Note that page rank is the rank/position your result will be displayed according to your page rank. for example if you had a restaurant and you could optimize it pretty well the result for "Lebanon restaurant" will display your website in the first page.
Page indexing is something else and could be optimized also in many ways:
Let's take this forum for example:
"http://forum.tayyar.org/f79/search-engine-optimization-smo-34803/"
This link is rewritten in mod-rewrite using an .htaccess file to redirect such links or could be said as fooling the crawlers by changing your pages from .php? to .html or slahes because crawlers have static pages as priority on dynamic ones and at the same time use the link to get a result when someone searches for "search engine optimization" which even if you remove from the link won't affect the page loading click here:
http://forum.tayyar.org/f79/i-love-mana2ish-34803/
In another meaning crawlers don't like the "?","&"
I just gave a small summary about it, it's something really huge and very profitable if you could really know how to do it :D