Just sneak a $50 note into the teacher's pocket and play it off like "Oh! How did that get there?" (Teachers aren't paid enough so its all for the greater good
In all seriousness though, It's fun to just strike up a conversations with teachers about what they did on the weekend, etc. As long as you don't get too annoying (like with one of my friends) it shows that you acknowledge that teachers are people too. But then again, I haven't given it all much thought yet.