The average character has only a few ways of recovering, such as jumping and an up special move.
However, some, such as Sora, have another way.

If you hold down the Up button when jumping in midair…

I-I can’t believe it! He’s flying!

In Smash, flying in this fashion is called gliding. It can be very helpful when you’re knocked off to the side.

Press up while gliding to turn upwards.

Alternatively, press down to dive downwards.

If you go far enough upwards…

You’ll cancel your flight.

Just be aware that you can’t turn around while gliding.

…Help!