Wavedash

By airdodging diagonally along the ground, you can reposition yourself without changing direction and while having full grounded actionability after just 10 frames of lag.

Fox's wavedash is about average in length, but its power projection is augmented by his amazing grounded moves: up-tilt, down-tilt, up smash, and shine. There are a practically unlimited number of uses for this technique; it is often used to grab ledge, feint opponents in neutral, and position yourself for follow-ups.

In addition to its pure form, many techniques build upon the fundamental element of the wavedash.

“ When wavedashing, you will sometimes hear about SH [short hop] when you wavedash. This is good, but in my opinion an even stronger optimization is to press both triggers, ensuring a frame perfect press regardless of polling nonsense, as an early press won’t do anything! This presumably makes worrying about SH WD unnecessary, but I’ll need to try it more to be confident. ”
— cookbook.gg

Practice acting out of wavedashes as quickly as possible, since you'll often use it to approach an enemy and put out a hitbox.