i have noticed that many instructors try to give the "proper" way to do things, then let them slide once in a while when they get going. almost everyone i have watched has said to set the seams when ironing, then just opened the pieces and pressed without setting. the same thing with removing the pins. ha ha. unfortunately for them, they are being watched by thousands on the internet and get caught.
i have been teaching a friend who has never quilted. we are part of a group. i try hard to give her the "correct" way to do things. after she is on her own she can develop her own bad habits.