resonance theory

How do you teach resonance?

During our review since last week, resonance was labeled as one of the most tricky concepts (along with electron pushing in my opinion), despite lots of practice and instruction. My teaching sequence consists of defining and providing examples of conjugation (after learning about hybridization), delocalized electrons, and finally pushing electrons if conjugation exists. I remember from teaching at the college level that resonance was also a tricky topic for many undergraduates.