The Skool of guitar excellence
Getting started...holding the guitar and the plectrum
Just before we start lets get comfortable with our guitar. Sit upright on a stool or chair with no arms (or the side of your bed) and rest the guitar on your right leg (if your right handed) supporting the neck of the guitar lightly with your left hand.
I say lightly because this hand must be free and unrestricted to slide up and down the full length of the neck. So take a minute and get comfortable with your guitar.
You may want to stand and play and it is a good idea to try this once in a while so as you get used to this position, particularly if you want to play in a band some day.
If so, make sure the guitar strap is properly adjusted to a position that allows you as much comfort as possible.
RockSkool: 5:Sitting Comfortably?
As a rule, the guitar should hang about the position it would be if you were sitting.
The guy in the picture seems to have it about right... although each person may have their own
preferences.
For now, I recommend sitting until you master some basic guitar techniques.