When I teach, I try to apply the law of witnesses: "in the mouth of two or three witnesses shall every word be established," (See D&C 6:28, 2 Corinthians 13:1, Deuteronomy 19:15, 2 Nephi 29:8, Matthew 18:16) to my Lesson preparation. The idea is that as teachers, we're always looking for "witnesses" to the word. When we establish the word with multiple witnesses, or testimonies, we help it sink deeply into the hearts of those we teach.
Here's how it works: Say I'm teaching on 2 Nephi 13. Nephi, the author of that book, is my first witness. I'm teaching directly from the scriptures, which means the Holy Ghost can be there. That's two witnesses. Now I'm looking for my third witness. Is it a cross-reference to another scripture? Have I had a personal experience with this topic? What questions can I ask that will cause my students to share their own witness? Is there something in General Conference that will help? How about a great quote or story?
All of these witnesses will bear testimony of the core truths in the passage, helping establish it with the power of the law of witnesses I find that my additional witnesses are most effective when it's my students who bear testimony. If I can get more than three witnesses, that's even better!
Repetition is a key way to help students learn. Using the law of witnesses establishes truth and helps students learn and retain teachings.