A. Sure, he's been doing it himself since he was a teenager and knows what he likes better than anyone but that's no excuse not to bother. Besides, I'm guessing that if he had to choose between a self-administered hand job and one from you, he'd choose your helping hand every time.
For him, the foundation of manual sex is the essential up-and-down technique. Think of it as creating a 'virtual vagina' with your hand. Grip his erect shaft in your strongest, well-lubed hand. Move your hand up and down the shaft in a fluid motion, never losing contact with it completely, and closing your grip as your top fingers pass the head. At first, work the entire length fairly slowly. Closer to orgasm, he may prefer you to focus on the top half, while picking up speed (when in doubt, just ask!) Start off with a light grip, then slowly increase firmness. Always keep the movement steady rather than jerky. You can add a slight back-and-forth twisting motion as you go up and down - you shouldn't be pulling the skin, just letting your light grip move smoothly over him. Later, get your other hand in on the action by alternating moves with each hand.
Don't be afraid to set up shop between his legs - that way, you'll have a lot of freedom to use both hands in a variety of positions. Plus, you get the scenic view, which includes his 'unit' (you can watch what you're doing and look for tell-tale signs of an impending orgasm, like his testicles pulling up into his body) and his face (great for reading facial expressions and making sexy eye contact). You can also kneel beside him, though in this position access to the penis's sensitive underside ridge will be limited. If you want to try another angle of approach, it's better - and dirtier - to kneel over his chest, especially if he's a 'bottom man', as he'll see you in all your glory. Now that's something he can't do himself!