Nice CG, my old college shop teacher tech would tell you what you were doing wrong by the number of “offenses”, I always loved that.
There are plenty of sources for tutorials, and if you looking for that in answer, you haven’t been looking very hard! As cg mentioned, the Gnomon Workshop stuff is great. Also check out my 5 minute sketch series: VIDEO>>>5 Minute sketch series
And other tutorials in our section: VIDEO>>>5 Minute sketch series
The brief DVD produced by our own ip_wirelessly is coming out and features several core77 regulars: http://thebriefdvd.com/
Design Studio press is never short on inspiration: http://designstudiopress.com/
I’m working on a book that covers some of the philosophical broad strokes. Have to love Blurb.com. I’ll let you all know when it is up: this list is a bit of the core of the book, expanded out of course: Is sketching important? - #47 by yo1
…As well as my thoughts on how we are wired for visual information and how visual language is almost universal, and how mastering that language takes considerable effort. It will have a little over 90 pages of sketches, most of them much lower fidelity than you see in many books, rougher initial exploration sketches, quick concept sketches with color blown on. I think it will be good, most books focus on the uber finished stuff, this focuses more on working level.