I prefer to do flavor hops around 20min and aroma at around 5min. I usually throw some hops in at 10min for hop heavy beer (APA, IPA). The flavor and aroma you get depends on the time, the hop, and the gravity of the beer. It's not an exact science.
You can use this chart as a rough estimate of what to expect.
Homer: “I’m feelin’ low, Apu. You got any of that beer that has candy floating in it, you know, Skittlebrau?”
Apu: “Such a product does not exist, sir! You must have dreamed it.”
Homer: “Oh. Well then just gimme a six-pack and a couple of bags of Skittles.”