By encouraging students to ask questions during lecture you can gain insights into parts of your explanation that were unclear and better understand what students find difficult about the topic. Ask students “What questions do you have?” rather than “Do you have any questions?” to set the expectation that questions are part of the learning process.
Example: "What was unclear? What questions do you have?"
See this and related tips as a Tip Sheet: http://csteachingtips.org/tips-for-lecturing