even in a masterclass with an informal setting, you can start teaching students about how to be professional. i mean, how to walk onto the stage (don't be shy now - walk boldly stuff - head up - smile at audience), how to grab hold on the one side of the piano and bow (some teachers have the students count according to the steps of this (bow, slight pause, return, turn, sit. for dvd's you could actually watch the stage presence of other pianists as they enter and leave the stage (only). this could be an entire master class believe it or not (when you have a whole class).
next, i think, is audience repore. some students alienate the audience by doing little things. i can't think exactly what i am trying to say yet, so this is short. not acknowledging applause is the one that most comes to mind. facial expressions. learning how to show feelings (if a piece is too metronomic). seeing oneself videotaped is really excellent because it teaches you the most. what you actually look like while playing. aiming for smooth actions is important (choppy or smooth?).
memorization - can be another thing they practice. to go up and attempt to play soley from memory. if they make a mistake (teach them about finding - in their heads- the next possible place to start again - and try not to let them get emotional). start teaching them, as in military school, to stick with it and not start crying or fall apart. you can make it less tense, too, by saying something about the chord they are on and which one follows (naming notes). if that doesn't work, and they don't find their place (go ahead and let them look at the music) - but for those students - often playing their piece twice would be advantageous. in fact, one of my teachers always had us play twice. first, the whole way through. then he would ask the audience (other students) well, what do you think? we each would give our opinions and encouragement. then, he would start in on a certain passage and help us play it better. then, we might just play a section (or the entire piece again - better).
lastly, the teacher i am thinking of always gave more credit to the students who came to every master class AND participated. you can't be shy. to overcome shyness, you have to learn step by step to overcome it. many youngers students don't like to feel embarrassed or humiliated. but, as you grow to adulthood, you realize you hit many of those situations in life anyway. why nto learn to deal with it. in fact, you could make it a practiced item (to teach how to accept valid criticism without becoming upset). and the types of criticism you won't allow from student to student (and, to build trust, from yourself). it should never be about the person, or in a joking manner, or to humiliate. always, to improve. and praise is helpful too.
then as your master classes go on for awhile, tell them to bring a friend. the more the merrier, right. the friend doesn't have to play piano. just be a warm body and make the pianist feel the same feelings they would in a recital. learning to handle nerves, stress, (as someone else mentioned in another thread - what to eat beforehand - what helps their nerves), how to handle mistakes that are unplanned or even tripping, proper shoes and clothing. (now that is an item by itself - shoes and clothing - especially with younger students!!)
i once wore some highheeled boots (thinking it would help me on the steinway because it was on rollers). i got majorly chewed out. he probably said something like, 'don't wear high heels when you play the piano. they make you unsteady and unable to control the piano pedals. wear low heels') something my current teacher does, is choose shoes that are wide toed. i didn't ask specifically, but image this keeps you on the pedal and not sliding off. also, you don't want slippery soles. it is very unnerving in the winter and on slippery stages. (you can buy those rubber plastic soles and stick them on).
hope this helps!
ps i found some black pumps at a regular dept. store that had the wide toe and LOVE playing in them. they are low heeled and i feel steady and able not just to play the piano, but to walk on stage (without worrying about your ankles) steadily. it gives you more confidence.
another item for discussion is strengthening your back. extremely important to pianists and often left undiscussed. you could even hand out those regular back strengthening exercises handed out by chiropractors. if every pianist did these, they would at least have some strength (even without working out). if the kids were my own, the exercises would be mandatory to playing the piano. you can really damage your back sitting for long periods without taking care of your back.
oh, and another thing is those taubman videos about relaxation. a lot of good stuff.
and, you could add in about the history of certain pieces or more about the composer. one of my teachers used to even give a little quiz afterwards to see what people remembered about what he said on very many different topics. sometimes he would hand out just general info, or funny polls (kind of like on piano forum). it's good to have humor too, sometimes, and hear a joke. it warms up students who look really stressed before they play.
Topic: Have you ever taught a master class ?