I found early on in my teaching that asking questions of random students through out the class, rather than wait for them to ask questions, was a much more effective strategy for keeping the students focused and engaged. The trick is asking the RIGHT questions.
I found this article: Blooms’ Critical Thinking Questions to Use In Class and thought I would pass it on. I like that there is a link to a pdf with the chart in the article. Using the questions from the various boxes will definitely challenge students to a higher level of thinking and should produce a more interesting classroom experience for everyone.