In one of our web products we have ‘hot keys’ to allow a customer service rep to maneuver quickly to a specific function without using the mouse. We have a series of tabs in the customer screen which allow the customer service rep to access different pieces of information about the customer. Each tab currently has an Alt sequence attached to it (ie. Alt + 1). We’re at the point where we now potentially have 10 tabs and Alt +10 isn’t going to work, neither is Alt +0 because it is already assigned. What is the Best Practice for hotkeys?
I don't think hotkeys are going to work well for this kind of action.
To call a tab with a hotkey, a user must know the number of the tab they want. Memorizing more than a couple of tab numbers is going to be difficult, because human working memory is limited at around seven chunks, and you're going to need to reserve at least four or five for the user's actions in the interface (assuming users aren't multitasking).
If a user doesn't know the number, they'll have to look for it first, in which case, it'll be quicker for them to simply click the tab that they desire.
If you want to use accelerators, use them in such a way that a particular hotkey will always bring up a certain kind of content, no matter which tabs are open. For instance, Alt+3 should always give focus to a 'history' tab for the current object, opening 'history' if it isn't already. Users can therefore commit the hotkey to long-term memory, rather than relying on working memory instead.
If your application is fast and tabs load quickly or instantaneously...you could just have two shortcuts - next tab and previous tab. Maybe bind it to the arrow keys.