There are several good Instructables with crochet patterns that show you how to use granny squares to make afghans, hats, scarves, bags etc. However, I did not see one on how to make a granny square. I hope this Instructable will fit the bill.
Cardigan and Sweater in King Cole Merino Blend DK - Discover more Patterns by King Cole at LoveKnitting. The world& largest range of knitting supplies - we stock patterns, yarn, needles and books from all of your favourite brands.