Including everyone is as simple as asking each person one thing that made them happy that week--just remind them to keep it brief, especially if you have a large class!
Sharing is always fun. I ask the young women after reading a scripture or story, "Have you ever had an experience like this?" and almost always the answer is yes! It's great to hear them apply the doctrine in their lives.
Calling the youth by name is a great way to help everyone pay attention. It helps them realize that you expect participation from them and makes them feel important. Because they are!
Listening is huge. When your youth answer a question, acknowledge that they have done so. There is nothing worse ignoring a person who responds to your query. A simple, "good job" doesn't cut it. Allow room for discussion; ask them, "How did that make you feel?" or something similar. Don't immediately move on to the next thing. Respond to what they said, and if possible tie it into the lesson by saying something like, "I like that because it applies..." or "We are talking about that next in this scripture...." or "Can anyone think of another example like this?"
Challenging the youth is my next favorite. Challenge them to choose one thing from the doctrine to apply in their lives throughout the coming week. Have them write it down!
What else do you find helpful? PS. These tips can also be applied to your adult classes!