The most important thing is to be flexible for each client's needs. Overall, I try to focus on interface design and usability skills and issues, not tools and technologies. Many people point to the Microsoft Office suite of products as the interface model they should be designing toward. However, just because a product has market share does not mean it is as usable as it could be. It follows a real-world, practical metaphor that people can understand.
People are incredibly adaptable, yet at the same time, they are incredibly resistant to change.
You have to be careful when you ask users what they want. What You Know Is What You Like. Also, don't assume that you are dumb if you can't figure something out. If something is confusing, it's usually the designer's fault, not the user's. One, people usually overrate their own computing skills.