C.J. Miles doesn't have one specific area that jumps out at you when watching him play. He is a fairly well-rounded player that can do a lot of different things well, and has a nice feel for the game.
The first thing you will notice about Miles is the smooth way that he moves around the floor. While he isn't blessed with a blow-by first step, or rim-rocking explosiveness as a leaper, Miles has very nice body control and is always shifting past defenders. In this area, you might compare him to a Ray Allen
You might also think of Allen when you see his body type. Miles comes in about 6'5 (maybe 6'6), and has very long arms. Despite having a quite frail upper body, Miles' arms and body control allow him to be a very effective rebounder from the SG position.
Miles' main strength at this point is probably his outside shot. He is a great natural shooter, and has very nice range on his shot. It's his shooting ability that allows him to get by defenders off the dribble, and pull up for midrange jumpers. When Miles does attempt to attack the basket, he has proven reasonably effective at this.
There has been talk of Miles playing some PG if he was to pull out of the draft and attend Texas, and he does have some ball handling ability. While he certainly doesn't have the handle or quickness to ever be considered even a combo guard, he does look comfortable with the ball in his hands, and his size allows him to see the court well.
While it is always hard to project how a high school kid defends on the NBA level, Miles has some decent natural tools here as well. His smooth athleticism and long arms could translate into something successful down the road. Miles appears willing to play hard on the defensive end as well, always something nice to see from a high school kid.