In the other, never log in to Google services.
That is more complicated than that, Google Analytics is used in waaaaaay to many big and small sites. You won't tell Google what you visit, but the sites themselves will. Google will see the same IP address is visiting a Google Analytics site and using GMail, and that can can be used by their ad casting machine. Try the NoScript add-on on Firefox to see how many sites tell Big Brother that you just visited them. It's jaw dropping.