When starting out on guitar and teaching yourself it can be easy to pick-up bad habits in posture and playing position because you do not have a teacher to see and correct these small issues. At the beginning you won’t be able to tell if how you are sitting or holding the guitar is slightly off.
If you don’t get these things right early then you will have to unlearn them later on and it will also slow down your progress because you will unknowingly be making things more difficult for yourself.
Nate Savage from Guitarlessons.com has put together a great series of videos to help the beginner guitarist with just that.
He also tells your what the different parts of the guitar are and all their names, and the note names of each string.
And you will learn how to tune the guitar with a tuner and by ear, basic right hand an left hand technique and some beginner chords.
Nate has created a great 12 video series for beginner guitarists. If you are just starting out and follow these videos from the beginning I can guarantee you will progress faster and avoid some common bad habits.