In the 37signals book rework they mention finding ones Epicenter, the one thing your business must have to survive.
They use the example of a hot dog stand and the guy needing at least the hot dog to have a business even if he is lacking everything else that people "may" want.
Now my business is IT services I repair personal and business computers, setup networks, create webpages, and train and support staff.
So I feel like my epicenter would be to provide IT services.
However I feel this is too broad.