I used to use different browsers to maintain different logins. I’d use Chrome for my personal Gmail, Firefox for my work email, and Internet Explorer (eww) or Safari for my work login (to access Google Analytics and Google/Bing Webmaster Tools).
Now I just use Chrome. There are several ways to accomplish this. I’ll demonstrate the easiest:
Step 1: Log in to one of your Google accounts in Chrome.
Step 2: Open a new tab.
Step 3: You’ll see your email address in the upper-right corner of the browser. Click on that. (It doesn’t look like a link but it is.)
Step 4: You’ll be prompted to sign in.
Step 5: Once you’ve logged in, you’ll have the option to import bookmarks and install extensions. (You’ll start from scratch with each new user you set up, and it doesn’t appear you have the ability to import extensions, which is unfortunate. They should be be imported when you sign into an account, in my opinion.)
Step 6: Next, you’ll have the option to name your login and assign an avatar to go with it. You can’t customize them, but you have a few options to choose from.
Step 7: Once you get set up, you can easily toggle between your different accounts by clicking on the avatars in the upper-left corner (Mac: upper-right corner).