I have at least seven Google accounts. I have a personal account, a school account, an old school account, an official Brookhouser trainer account, an account I use for the school's YouTube channel, an account I use when I volunteer for the SPCA for Monterey County, and a few that were created for me when I was training others in their own domains.
I only use three of them on a daily basis: personal, school, and school's YouTube channel, but I do use them daily. My workflow had been Chrome for personal, Firefox for school, and Safari for YouTube. That way I could stay signed in without logging in and logging out over and over again. Yes, Google does allow multiple sign-ins in a single browser, but I don't recommend it.
Then on the Google Educast, Sean Williams, Chris Betcher, and Diane Main taught me to create "multiple instances" in Chrome. See the clip here. Since I followed their instructions, the entire way I interact with Google has changed and become more efficient.
Now when I am using my personal account, I see a frightening faceless orange avatar in the corner of my screen. It would be less scary if he weren't so shiny.
And when I'm using my York account, the face is York red.
Still scary, but easily identifiable, I guess. They remind me of this guy.
Here is a video I made for my colleagues that shows how to manage multiple Google accounts using Chrome.