In my opinion the best way to learn drawing is the triangulation method (lesson B12 for those of you who are members of the Virtual Art Academy). I personally think other methods commonly taught (such as contour drawing) actually make it much harder for you to learn. In fact I think they actually prevent you from learning how to draw really accurately. I suggest you just get this book from Wiley publishers which explains the method pretty well. The book is called "Drawing in the Digital Age". Here is a link
to it. It is basically the same method I now teach to all my students in the Virtual Art Academy program, and I have just started to use this book as my course textbook. It takes just about a week to learn how to draw quite well using this method. I hope this helps.
My drawing of a Tibetan woman in Bamei, Sichuan, China. I used the triangulation method on this portrait.