1. Never promise something you can't deliver.
2. If you don't know something, admit it. Never try and pretend you know something you don't.
3. Complaints are GOLD. If a student has a complaint or concern, treat it as such. For every student that has a serious complaint about your dojo, the teaching, whatever, there are 10 other students who are thinking it and don't have the guts to say it.
4. You are not the grand dispenser of knowledge. Any good instructor is nothing more than a senior STUDENT.