Google measures average time on site by first collecting each visitor’s exact time on a particular page. Imagine that a visitor lands on page 1 of your site. Google places a cookie, including a unique code for the visitor and a time stamp. When that visitor clicks through to page 2 of your site, Google again notes the time, and then subtracts the time that the visitor arrived at page 2 from the time that the visitor arrived at page 1. Google then averages each and every page’s time spent to get the average time each visitor spends on the site.
Hey Jym, thanks a bunch :) Yeah, I don't think everyone need to use each and every one of these, especially at the beginning. But I do find the list useful for those with "older" blogs. When you are thinking "Where else can I go to get more people to see my blog". That is what I do with my first website. Again, I agree with the part of identifying the ones that will work the best, so we don't spend too much time getting no results. Thanks so much for the comment