1) Pretending they don't know what numbers are.
Not all instructors do this, but enough do it that it needs to be addressed. You'll be doing pushups or whatever, and the instructor will say "Four more!". You'll prepare yourself mentally, rationing your energy so as to complete those last four to the best of your ability. And the smartass instructor will go "Four, three, two, two, two, two, two...aaaaaand ONE!" and then she'll laugh.
Well, I refuse to participate in her sick games. As soon as I've completed my four, I simply stop and stare at her until she's done pretending to be an idiot who can't count. I urge you to do as I do. Eventually the instructors will get the hint and stop trying to fuck with our heads.
2) Insisting that students whoop and holler like trailer trash.
Every. Single. Instructor. Does this. (Except yoga instructors, obviously.) At some point during the class, the instructor will say "Wow. You're all so quiet today!". Because instructors are an extroverted bunch, and they become intensely uncomfortable with the slightest bit of quiet. They need constant validation from their students that they are, in fact, enjoying themselves, and unless the students clap and carry on like drunks, the instructors feel blank and hollow inside.
Dear Instructors: We do enjoy your class. If we didn't we wouldn't come. Not everyone likes to scream and shout, especially not when we're sweaty and breathless from exertion. Learn to love yourself, Dear Instructor. Your self esteem will shine from within, and it will draw us toward you, like moths to a flame.
Or, you know, at least let us maintain what's left of our dignity.
3) Insisting that we need to burn off the claories from whatever holiday has happened recently.
I kid you not - in February, I had to hear about working off the Valentine's Day chocolate until FEBRUARY 28TH. No one eats so much chocolate on Valentines Day that they are still working it off weeks later. Or rather, the people who eat that much chocolate are probably not hanging out at the gym much. But it's also Christmas, Thanksgiving, Fourth of July, Labor Day, whatever. You can bet that if there's been a holiday within a week of the class you're taking, every instructor will make the same lame ass corny joke about how we need to burn off those Black History Month calories or whatever. Stop it, Instructors. Stop it!
4)Instructing us how to smile.
"OK, now extend from the elbow. And press. Press. Press. And press. Now lift. Lift. Lift and lift. Now bend the knees. And hold. Pulse. Pulse. And turn the corners of your mouth up." Then shel'll smile at her little joke. She's tricked us into smiling! Isn't that precious?
Dear Instructor: We aren't smiling for a reason. You are hurting us. We are in physical pain. Tricking us into smiling will only make us hate you. It is not helpful. It burns no calories. Just let us be.