There are two key rules that make work manageable:
1) All work is done on a Service Ticket. That means we don't do anything until there's a ticket.
2) We do all work based on it's priority. When everyone is working on the highest priority work they can do, then everything runs much smoother.
Strangely enough, some people don't like to prioritize tickets because they're afraid that the low priority tickets won't get any attention. Think about what that really means. If you're so backlogged that some things won't get done . . . Do you want those things to be low priority or high priority?
If you don't work based on priorities, you are wasting a lot of time, and dropping the ball on some important stuff.