Silentbear, although you're right about the natural sugar making a man taste sweeter, chocolate will actually make you taste bitter. Pineapple and citrus fruit is probably the best. Basically if your mister eats a healthy diet, he's liable to taste better or be tasteless.
As for technique, deep throating is hard. Eiri is right, you can bruise the back of your throat, and it's painful. Don't let him thrust into your mouth like he does your vagina, because you might throw up. There's this thing called a gag reflex
Some people overcome it, some people have a really sensitive gag reflex.
With deep throating the guys only really like it because every body says it feels the best. It's actually the same sensation as if you pursed your lips and pushed his head through them while gripping his shaft. It's really up to you.
You could also twist your head as you're going down his shaft. My man loves that. the sensation is great, and it's probably the same motion when he masturbates. Watch him masturbate, it's a great way to find out how he pleases himself and what feels best for him.
Other than that, when you're going down on him enjoy it. I love every inch of my man's penis, and I let him see and feel that. He should reciprocate when he's going down on you.