I'm self-taught and preparing for interviews. My primary focus is to study/learn data structures and algorithms since they seem standard for most programming interviews. I'm pretty comfortable with C#/.NET "trivia" questions, and also javascript and sql.

What types of design pattern questions are typically asked? Are the questions mostly discussion-oriented or are interviewees expected to code and/or draw the UML diagrams?

My approach right now is to focus on the ones that I can easily identify and/or have used. This boils down to the factory, singleton, decorator, mediator, iterator, observer, and a few others. So maybe one-half of the original GOF plus a few widely-used non-GOF patterns (repository, dependency injection, MVC, etc.)