I've started a series of posts called Guitar at Work (or School) where I'll be sharing things you can do while sitting at a desk, during your lunch break, or even while watching TV, to help improve different aspects of guitar playing. Week 1 is on posture.
Good posture is a basic element of guitar playing and is very important regarding the long term effect it will have on your back, shoulders, etc. If you're a beginner guitarist, you may find yourself wanting to lean over the top of the guitar to see the frets and your fingers, that will only hinder you're guitar playing and, as crazy as it sounds, could cause injury. When you are playing and you look down you should mostly see the side of the neck, otherwise you'll be wasting those magical fret markers that they put there.