Getting to know your users means getting to know their motivations and goals. A common pitfall is to focus on tasks that users engage in, rather than their goals in performing those tasks. Real insight into these topics is difficult to achieve through data from surveys alone; you need to venture out and talk to users directly.
About Face (the book I recommended in a comment to your question) phrases it quite eloquently:
Any attempt to reduce human behavior to statistics is likely to
overlook important nuances, which can make an enormous difference to
the design of products. Quantitative research can only answer
questions about “how much” or “how many” along a few reductive axes.
Qualitative research can tell you about what, how, and why in rich
detail that is reflective of the actual complexities of real human
situations. Social scientists have long realized that human behaviors
are too complex and subject to too many variables to rely solely on
quantitative data to understand them.
Two ways to get the information you need:
- User interviews
- User observation (shadowing)
If you are redesigning or refining an existing product, it is
important to speak to both current and potential users. If you start fresh, you'll have to seek out people that match your potential users' goals. While interviewing them, it's important to get a feeling for the context of how the product is/will be used. You need to know when, why, and how the product is or will be used. You'll also get a better grasp about expectations, problems and perhaps even frustrations that exist.
Most people don't really quite know how they use a product if they're telling you about it. That's perfectly normal. That's why it's a good idea to shadow a user; you'll get the benefit of context of use, and there is no risk of users omitting information in their answer in fear of looking dumb. Observe the user in their normal work environment, or whatever physical context is appropriate for the product. Observing users as they perform activities and questioning them in their own environment can bring the all-important details of their behaviors to light. You won't have to interpret actions later. So, rather than coming to interviews with a set questionnaire, you can directly ask questions and capture all the relevant data. The user will tell you (directly or indirectly) what you need to know. Look up contextual inquiry for more information.
Once you've finished up your initial research, you should have a set of behavior patterns. These patterns suggest goals and motivations (specific and general desired outcomes of using the product). For consumer products, they tend to correspond to lifestyle choices. Behavior patterns and the goals associated with them drive the creation of personas.
Design requires a target — the audience who is most serviced by your design. Typically, the more specific the target, the better. This is called a persona; it's a made up person who encompasses the behaviour, motivation and goals of your actual user. Sometimes (when your product is not very complex), one persona will suffice. Usually you'll need more than one. Prioritize your personas to determine which should be the primary design target. The goal is to find a single persona from the set whose needs and goals can be completely and happily satisfied by a single interface without disenfranchising any of the other personas.
You'll use these persona's to talk with stakeholders about your design. So if someone asks you "what can you tell me about who's going to be using this application?", you'll reference to your persona.