Learn lots of mindgames and movement tricks. Not all of them are helpful, but the idea is to get used to Fox's movements and being able to be fluid (i.e. Not messing up wavedashes, short hop mastery, rshl instead of illusion to selfdestruct). Eventually you'll be able to fake people out with stuff like circle jumping or jump stops.
Now, you don't need to learn A LOT, but a good few to keep yourself moving and unpredictable. You're playing Fox, which is a fox. Be sly.
Ex. I noticed that whenever I play my sister, she rolls when I short hop toward her, because I usually use a shffl when I do, so instead of attacking, I decided this time to waveland/air dodge backwards (I say this b/c I suck at wavelands). Guess what? She fell for it and I was right next to her, ready to punish...sort of. You see, I wasn't very good at circle jumps and the other movements other than attacking and combos, so I wasn't used to these situations and doing these kinds of movements, therefore, I was sloppy on the follow up and she got away...and hit me.
