What are some key UI design tips that every developer should know?

While there are a number of UI resources for developers (for example, Joel Spolsky's User Interface Design for Programmers), I'm interested in more of a bullet list that can be communicated in 1 to 2 pages.

I'm interested in more tactical, day-to-day UI tips, as opposed to overarching UI design goals that would be covered in a UI design meeting (presumably attended by at least one person with a good UI sense). A collection of these tips might cover about 80% of the cases that an everyday programmer would come across.