I know this is one of the most difficult things in site building. How to get to the top of Googles seachresults. At least a position on page 1, 2 or 3 would be nice ;)
I build a clean site without any tricks, and only use Yoast's SEO plugin. The site was doing very well, but suddenly it dropped from pagerank 4 to 1 and when searching I have to click through to page 10 or further to find anything, while the is being refreshed every day with at least three pages. I made a sitemap and this is indexed completely by google.
If you have time, take a look at the site and report anything you thinkg might be wrong: http://www.bt10.nl