What to put in a thank you note for a teacher? Answer soon please!?

Say this "You're a great person" or mention something that he does that is simple and sweet and how you appreciate it. For example, if he writes notes on his graded papers say, "your messages on our graded papers are sometimes irritating, but are also very helpful- and I appreciate you for this. Thankyou" This is simple, sincere, and funny and (I think) he would like that. Good luck!!