I am just starting acoustic guitar lessons. I keep picking the wrong string. My left hand has a finger holding down a string against a fret but I keep striking the wrong string with my pick. My trainer says to keep the guitar up against my stomach which doesn’t allow me to see which string is being plucked. Is there a way to determine which string is which with my right hand?
I advocate students resting the edge of their picking hand palm (next to pinky) just past the saddles on the bridge. It won't mute the strings, but will provide an anchor, so movement across the strings is limited to the pick being able to move by a smaller amount. The problem will go away after a while, with lots of playing done, but in the meantime, don't let the hand float around.
"Anchoring" your pinky finger might help (For fingerstyle guitar, is anchoring your pinky on the guitar bad?). I use quotes because the word makes you think that your finger should be glued to the body of the guitar, when it actually has some freedom and moves slightly along with the hand, not being tensioned at all (the idea that the finger is tensioned and unable to move, stretched out and stuck on a spot, makes the practice be unfairly frowned upon by some people).
An alternative to anchoring your hand would be to practice feeling the strings. Try sitting down, ditching the pick for now, closing your eyes, and feeling the strings with your fingers. Try fretting a string with your left hand and figuring out which string this is with your right, plucking it with your thumb as if your thumb was a pick. You should start to feel instinctively where the strings are.
I'm in the "don't let your hand touch the face" side. While letting the student find a relative position to the strings by touching the guitar in some way may speed up finding the strings, I've seen too many students develop their technique to require their hand touch the guitar to be able to find the strings.
This limits their progression of good floating hand technique, and creates a situation where they have an ingrained habit that they have to now break to be able to progress.
Although it may take the student longer to learn, I prefer that the student spend exercise and practice time finding the strings from a floating position. Usually I use the exercise of fingering a chord (Em for starters) and playing each string top to bottom with a down/up picking. With beginning students I also have them "warm up" by playing each string down/up while saying the name of the strings. Eventually we'll switch to playing every other string while playing the chord.
When the student is working on single notes, I have them play which ever string they land on, even if it is the incorrect one for the string they are fingering. With repetition it usually doesn't take long for the student to start finding the string their finger is on. It is important that they don't stop the phrase if they are on the wrong string, but continue to play out the passage. On the next pass they can correct which string they are on.
I agree with both answers here, when picking with a pick, I often rest my pinky against my high E-string, it makes it easy for reference. practicing while sitting in a comfortable pose will make this a lot easier after a while. Try doing practice drills where you change strings often, and after a while this won't be a problem anymore.
My trainer says to keep the guitar up against my stomach which doesn’t allow me to see which string is being plucked.
You should not be relying on your eyes to play - you want to develop the muscle memory in both hands to be able to play what you want without looking at the instrument. Your instinct is correct - you should be able "to determine which string is which" without looking. More than that, you should be able to play the right string without having to "determine" anything.
I'm agnostic on the question of anchoring versus floating right hand - personally, I know players better than me who use both techniques, so I'm not going to say one is inherently better or worse than the other. Whichever technique you use, it's clear that you need to practice your right hand technique. I suggest you start by aiming to play a given note on a given string, on demand, without looking. For example, your teacher might say "D, on the A string" and you'd naturally play the fifth fret of the A string.
From there, you might move on to playing good old scales in various modes and positions, without looking at the strings. A good interim goal to resolve your current problem would be to be able to have someone (your teacher, for example) say "B-flat dorian" and play that scale, obviously without visual reference to the fretboard.
Doing this sort of exercise should get you sorted - it sounds like you just have to make some mistakes.
EDIT: Thinking about the anchored vs. floating debate, if you use a floating right hand it's useful to ensure that your guitar is always in the same location relative to your torso. If you use a strap, that should help. If you play seated, try to keep a consistent seat height so that your leg is at the same angle, and your guitar is therefore in a consistent position.
As a guitar teacher, some thoughts from my experience that may help:
The OP says "I am just starting…" I would encourage a beginner student not to beat himself up over mistakes. We are talking here about muscle memory which by its very nature takes time to master.
Start with really simple exercises and repeat them over and over. Repetition is really the only way to learn string positions.
Start also with picking exercises using only the open strings. The OP refers to pressing a string with the left hand. This means a split focus: it's harder to concentrate on the right hand when I'm thinking about the left hand as well.
Here's a sample exercise that I might use. It only involves playing a series of notes on a single string. Most of my experience is with finger picking whereas the OP refers to using a pick. But the principles are the same.
If fingerpicking, the exercise is played by plucking alternating notes with the first and second finger.. If using a pick, the exercise is played using alternating down and up strokes.
To play this exercise I would get my student to focus just on the movement of his right hand. When he is clear on the correct movements (even if he can't yet play them) I would get him to play the exercise over and over again. The speed at this point is whatever speed results in correct playing. To start with, I would get him to look at his hand if necessary, but after a few bars I would suggest that he shuts his eyes. He will find that the first time he will make a quick mistake. But soon he will be able to continue the exercise for several bars before making a mistake. The number of correct bars is a measure of the progress being made.
Once the first exercise is reasonably reliable, start to add other exercises. A simple example for a pick would be to expand exercise one to pairs of strings as follows:
and so on. The process for learning these exercises would be the same as for the first exercise.