I have trouble positioning the mouthpiece one my lips. If someone could explain the standard embouchure to me, especially how much upper and lower lip should be exposed that would be great. I have somewhat large lips so part of my lips will prob. be exposed. Please Help me my band director doesn`t understand what i`m asking, because sometimes i play ok then sometimes i don`t. My embouchure is all over the place.

read the arban`s book paragraphs about embouchure. it gives the best advice

place your lips as in saying the word DIMMMMM your lips should stay in the "mmmmmm" position, began by buzzing a concert Bb on just the mouthpiece then begin working on the first few pages of the Arban, make sure you ARE NOT spreading your aperture and make sure you are fluidly tonguing the notes.