I am just beginning to do what many of you have been doing for years.... I'm tracking my keyword rankings on Google, Yahoo and Bing with the plan of trying to improve my rankings through on-page optimization (part of an overall plan).
1. How long does it take for on-page changes to effect KW rankings?
2. After the rankings update, should I immediately try to change low ranking pages, or is it better to wait some time between changes?
1. A couple of weeks usually, sometimes less, sometimes more.
2. You can try. It may or may not have much of an effect. I'd try building another web page and linking it to the troubled one first. Wait a couple weeks. Then do on-page optimization, wait, then build another page with different links naturally flowing from unique content, wait, then optimzation ...