Who is the typical consumer for your product?
Lotta different ways to research this one. (update: watch the overall training video here. )
There is a great series called Who's Buying (just about anything). Most of these are located behind the reference desk.
Can't miss the Best Customers book.
Local Market Analyst is a good source.
Simply Map is a good source for seeing how consumers in your geographic area behave. Tutorial here.
MRI+ breaks this down. Watch the training video. This is a way to get some online data from a reliable source.
Don't forget to get the macropicture of your industry with industry surveys.