There are basic rules to follow for SEO, and then there are labor intensive site promotion activities that you can do on a daily basis that add tiny increments that over time eventually add up to a boost.
The ROI curve for these time-intensive activities is, in my experience, not linear. There's a point at which you could easily devote 8 hours a day to pumping your sites and yet see very little return for it.
How much time do you spend, and what routine do you follow for SEO?
I think there are 2 aspects to SEO
For SEO external our site we have 1 employee who spends around 10-15 hours a week for a group of sites that gets about 1,000 hits per day.
The SEO within our site is more or less my full time job. That isn't to say that I only pay attention to SEO but when building functions, features, and updating the site I take SEO into consideration on almost every phase and step. We updated our site recently and just cleaning up our HTML and organizing our data better increased our site hits by over 10%.
