Basics.

Akuma is a near broken character, if played flawlessly you should be able to beat anyone using Akuma. However, his damage penalty is massive, as Akuma you take huge damage compared to any other character so he is probably only suitable for experienced players.

Akuma has rather bizarre hit boxes compared to most of the other characters, so you can hit more than you normally shouldn't be able to - and you can't be hit sometimes when you probably should be able to.

Akuma's Hurricane kick juggles, has massive damage and has great priority. It can be used to cross your opponents up to great effect.

Normally a Dragon Punch has a few frames of vulnerability, Akuma's is fully invincible all the way up, and it doesn't matter which button you press to activate it - light, medium, heavy - all fully invincible on the way up.

Air Fireball, using Akuma's Air Fireball it's possible to cross-up people in an inescapable trap. It also makes it hard for people to jump in at you. his ground fireballs have oddball hitboxes and the red fireball can three hit combo if done with a heavy punch.

Akuma's teleport is a nice move for showboating, but really as he stands he doesn't need it.

Akuma's Super special is one of the most powerful moves in the game, you can tick into it, once you have the button press sorted - making it nearly inescapable. It does half an energy bar of damage and if timed right can go through fireballs.

The rule of thumb for playing Akuma is to be cautious and avoid being hit if at all possible. His damage penalty makes this essential and his array of moves make this possible if you are good enough.