Learning The A Chord
Let's break down and practice the full version of the A chord. It's not easy, so be patient with yourself and your fingers.
Locate the 2nd fret of our D string. Now place your middle finger in that fret. Locate the 2nd fret of the G-string. Place your ring finger in that fret. Finally, find the 2nd fret of the B-string. Place your pinky there.
Try strumming all six strings. Sounds totally fine, but a lot of people prefer to avoid the low E-string. But don't worry too much about that for right now!
I play these three notes with my middle, ring and pinky, because my fingers are quite large and it makes it easier for me to cram them all into the same fret. Some people prefer to use their index, middle and ring fingers and that's fine as well!
Once you've gotten your fingers in place for the A major chord, let's try picking each of the strings individually or a few at a time. Make sure they're all ringing, and if they're not it's because one of your fretting fingers is muting the adjacent string.