Open string harmonics have a nice chime or bell like sound. To play an open string harmonic, lightly rest the tip of your finger on a string just above a fret wire without actually pressing down, then pick the string. It may take a couple of tries at first but when you succeed the harmonic is on mistakable. The easiest frets to sound an open string harmonic are 5,7,12 on every string but every fret has them if you hit it just right. You can also learn how to tune a guitar using harmonics.
A far as the other learning material goes (books and DVD) they both looked fine as far as readability and simplicity. Right off the bat, I did feel as though the whole learning system is more geared towards children (which I’m sure it mostly is) rather than adults. This comes from the color scheme, overall look and feel of the learning material, DVD content etc. Now don’t get me wrong, that doesn’t mean adults can’t use this product, it’s just an observation that I noticed during my first impressions.
As a beginner, it is best to avoid making a pawn shop, flea market, or yard sale purchase unless you are shopping with somebody who has experience in purchasing a guitar. Having never purchased a guitar, you may not know what to look for in terms of damage or guitar quality. With that being said, a local music retail shop is your best bet. You may also shop online with a reputable company, although be sure to review the business’ return policy.