
Talking to and observing users is invaluable to uncovering what customers really need and want. Good user research asks the right questions of customers and helps create clear business goals. Clear business goals lead to better designs and happier customers.
Based on user research, use cases document the ideal experience that people will have with your product or application.
Walking through your current product and documenting problems, as well as good things, further clarifies where resources and time need to be spent. The evaluation should rank the problems both in priority to fix for the user and how easy they are to fix. It's also helpful to do a documented walk through of your competitor's products.

Everybody needs structure, especially information rich sites and complex systems. I have created site maps and task flows strong enough to hold up under pressure and flexible enough to allow for unlimited growth.
I usually start exploring information & interaction design in low fidelity wireframes which are quick to create and easy to test.
Interaction design is how people experience your application whenever they try to do anything with it. How will people enter information? How does the application react to them when they click a button?
Information design takes all that great data and information you have and creates an engaging way to explore it. For instance, a graph is more interesting and easier to understand than a spreadsheet.
Good visual design makes things more enjoyable, usable, and communicates your brand to your customers. I work with brand designers to make sure look and feel, layout, and illustrations enhance the user experience and increase usability.

It doesn't have to be big and expensive, but it does need to be done. This is where you find out if things are working and get insight from real customers about why it is or isn't working. There is always room for improvement and my projects have always been better when even a small amount of usability testing is done.