There is a very common misconception that studying with a teacher means you will be put into a mold & forced to learn in a way that is not consistent with your goals. This comes with ideas like, “there is one right, formal way to play guitar, but if I learn to play like that, I won’t be able to make the music I want to make.” If this were true, there would be no reason to take lessons. In fact, depending on the teacher, this is often not true at all. I personally believe that there is no “right” way to play the guitar.
That being said, it is a balance. A true beginner does not even know enough about guitar to make their own goals, so I have to start somewhere. There has to be some structure in the beginning, just for the sake of getting the student doing something. I don’t care if it’s sight-reading, or memorizing a song on one string. Goal number one is always “get the student playing something.” & in order to do that with a beginner, it is helpful to look at “right” & “wrong” ways to play guitar.
On the long term, however, I try to teach with only two constraints sound & efficiency.
Sound is about listening to yourself. For example I might ask a student if he or she is aware that they are allowing strings to ring out, when they might sound better silent. Many times students are not even aware of the sounds the strings are making. So I show them how they might correct it, but in doing so remind them that it is just a choice. “Let them ring if you want to, but learn to know when they’re ringing, & learn to control it so you can make them ring or make them silent at will.” The same things will go for control over rhythm, tone & anything else that effects the sounds you hear when you play.
Efficiency is about achieving the sound you want with the least amount of physical & mental effort. For example, when I see a student playing a passage of a piece in a way that is different from the way I might play it. I show the student my way of playing it. I show them that my hand is moving around less than their hand. Even though we are making near identical sounds, I am expending less effort to make it. Like with sound I tell the student, “there is no single “correct” way to play this passage, just more & less efficient ways. Play it the way you had it, if you want to, but understand the logic behind my way as well. It may help you when you want to play faster, or if you want this passage to come easier to you.” Often times there will even be two or more ways of playing something that are equally efficient physically.
An example of mental efficiency might be when a student is struggling with a fingering because he or she is looking at it as a standard scale form, while they might be opened up to looking at it as a chord form. Either way is correct, but sometimes a different perspective helps your mind better connect the sound you are going for with a fingering you already know.
There is no right & wrong beyond sound & efficiency.