This gallery illustrates well the nature of Giacometti’s drawings. You get a sense of his struggle by the way he goes over and over the lines creating in many cases quite dense drawings. It is interesting that his figures often have specific lines that bisect as if he is trying to make measurements in order to capture the form, which as a sculpture is what you might expect him to do. I find it interesting that many of the drawings of figures, and of the heads in particular, have a very skeletal quality about them as if the have been taken back to the bone structure, and that this is then carried over into many of his sculptures of figures. Is this about how he really sees people or about getting to the essence of the figure?
Some of his work can be seen at the Tate, London and I also found this video which, although it is in German, shows some great examples of his drawings and includes a sequence of Giacometti making a drawing.