This might be helpful but I don’t know if I’ll ever remember to do it this way… We’ll see.

Now, you can visit google.com/accounts and click the link next to “Multiple sign-in.” After you sign into your first account, you can sign in with up to two additional accounts from the new accounts menu in the upper right hand corner of Gmail, then easily toggle back and forth between them. You can even open multiple Gmail tabs — one for each of your accounts.

via Access two Gmail accounts at once in the same browser – Official Gmail Blog.