Show that you're disappointed in him when he messes up and praise him when he gets it right. Be consistent. Take away something he looks forward to (a party, a certain hobby), if he screws up. Don't stay mad. Show him that you still love him, despite the fact that you punished him. Only guilttrip to keep him in line, don't stay spiteful. And realize that he's not doing this to taunt you. Quite the opposite probably
Also realize that some things he will never learn. Being on time is hard for us. I for one don't have a concept of time, as I'm never present in this world almost. Focus is acquired in bursts. Short attention spam is part of our make-up unfortunately, unless it's something incredibly interesting, then we're obsessive almost, to then throw it all out after 3 weeks and start right over after a month. Doesn't mean you shouldn't still make these things part of the rules though. But see if his way, no matter how funky to you, gets the results you want. And if so, let him keep his method (I drove my mother mad with the way I studied for instance). Also make sure he's very clear on what the rules are. Also very important, at least, it was in my case, is explaining
why you don't want me to do something. Don't pull rank on me, but make me understand. My mom always said she 'spent a lot of saliva' on me, talking and convincing me
I never felt entitled, on the contrary. But I did feel suffocated by a world that didn't understand me. Self-reflection, including navel-studies are very important to us
My mother taught me this way, and I couldn't have wished for a better parent. But however perfect a mom she was, she was never able to teach me not to procrastinate, get up on time, fit in, or make me present in this world. It frustrated her to no end (she was an S though). I was on time, only because I knew she'd pick me up after a party and I didn't want her to worry, and because I knew that otherwise she'd take away my privileges.
The thing that always kept me most in line was knowing that I'd hurt her, or disappoint her as I cared deeply for her. We live to please. Just accept us for who we are
/end mushy rant