These instructions were made using the "old style" view of Torero Mail. We are working on replacing the screenshots, but the steps should be similar.
For most users, we strongly recommend you keep your Torero Mail and Gmail accounts in different browsers after the transition to Google Apps+ (GA+). For example, consider using Internet Explorer/Safari for your Torero Mail account and Firefox for your personal Gmail account. Keeping multiple accounts open in different tabs will no longer be straightforward after the transition - using multiple browsers is easy and will help you keep things straight.
Google does allow you to sign in to multiple accounts for certain products, but you must turn the setting on in your Torero Mail account. To do so, log in at http://toreromail.sandiego.edu. Once in your mail, click the gear icon in the upper right and select "Account Settings". Click the link for multiple sign in settings, then read the warnings and press OK.
Google has created this video to explain more about multiple sign ins:
You can read more on the Google Accounts Help for multiple sign-in.
(Portions of this article are courtesy Berkeley Lab Commons, 2011)