Where to start on a green horse?

I recently, and unexpectedly, obtained a young horse who has been ridden about 10 times, hardly even considered green! Although I am an experienced rider, I have never started training a horse from such a basic level. He is very calm for his age, but knows absolutly nothing really. I figure I should start with basic groundwork, then lunging, and then get more complex in his actual riding... does anyone have any tips for doing this kind of training? Any info would be helpful, Thanks