I suspect the best SEO here says very little while raking in $$$$ while the rest of us spout nonsense and worry about paying the rent.
SEO is a pretty simple process if you know the basics and use some common sense. The rest is using a few other techniques you learn along the way by testing etc.
If you have the budget to do it one of the better SEO companies I have first hand knowledge of is ACS SEO. They handle a lot of larger companies as well as Pepperjam has a division that does SEO. If you cannot afford to go with the big dogs then better off spending a lot of time researching here and do it yourself.