"Smart" teachers ask good questions. One good area to question involves finding your students' intellectually "fertile fields" to sow the "seeds of wisdom."
How do you locate those fields?
1. Ask questions (see the post linked to above). Asking good questions gauges student understanding and interests.
2. Do not allow the first "I don't know" to work. Many times, students use "I don't know" to get them "off the hook." When you get "I don't know" ask again using different language. Then ask again. Once you get three "I don't know" answers, it is probably genuine.
3. The point at which the student is truly "stumped" presents a potential area to explore. Of course, the real exploration is done by the student with you as the guide. Remember, if the answer or new skill presented by The "Stumped" Factor is particularly difficult for the student, help them focus on WHAT needs to be done to GET BETTER rather than WHY they are trying to learn it at all. Focusing on "what" and "getting better" will help maintain motivation when trying to do something fairly difficult or unknown.