Step Fifteen: Learn advanced techniques to further enhance your level of play. Movements like Dash-dancing and Wave-dashing can be incredibly helpful when used correctly. It is important to learn these if you ever want to bring your skill to a new level.
Step Eleven: Percentage. Be aware of it, a higher percentage may require you to be more careful even if you prefer to play aggressively. While as a lower percentage allows room for aggressive play.
Step Four: Choose what kind of style you like to play for your character or best suits him. Some characters can be either aggressive or defensive and some usually are better one way or the other, find a style that suits you and is easiest to adapt to.
Step One: Pick a Character and stick with it. This might seem like an extremely simple thing to do, but I have seen on more than one occasion of players switching from one character because they weren't good enough with them. Pick someone you find interesting or you feel comfortable playing, then give it time for your skill to progress.
Step Twelve: Understand your characters limits. Kinda like Step Two, you need to recognize what your characters is good at and focus on it, never try to use a character that is bad in a certain style you want to play in.
Step Seven: Never underestimate your opponent. This may seem like a simple rule, but it is extremely important. Characters like Jigglypuff and Kirby look harmless enough yet have devastating combo game and finishers.
This is my Area of Expertise, as well as my favorite hobby. It's a game called Super Smash Bros which is a fighting game in which you knock your opponent off the platform in order to win, the last fighter to remain standing is the winner.