Directional Influence
Directional Influence (abbrv. DI) is one of the most important techniques to master.
Normal DI
Normal DI is a method of altering your trajectory after being hit using input from the control stick. Note: Normal DI DOES NOT affect how fast/ how much knockback you recive, it merely changes the direction you are sent. The goal of this DI is to change the direction an attack sends you to make it less leathal. Because you are only changing the direction you are sent, DI makes the most impact when done perpendicular to the base knockback of an attack. For instance, if you would be hit by an attack that sends straight upwards, the most pronounced DI would be straight to the side. Note that in that situation, you're decreasing your chance of dying off the top by bending your trajectory away from the upward death zone. For attacks that would send you off the stage in a manner to kill you, try DIing upward so you are sent less to the side, and more upward.
DI also helps to prevent combos. If you DI away from your opponent's weak attacks, they'll have a harder time following their attacks up.
DI is a difficult aspect of the game to master. It can keep you alive longer, it can keep you from getting comboed, and moreover, good DI makes you significantly better overall.
Smash DI
Smash DI (aka SDI) is something significantly different from normal DI. During hitlag (if you're being hit), if you input one of the 8 most cardinal directions on the control stick, you will get an instantaneous change in position in the direction you input. This is good for escaping multiple hit attacks such as MK's neutral/ Side B attacks, fox's uair, many of Lucas' attacks, etc... Note: SDI can only be performed with the control stick, not with the C-Stick.
Note: You cannot SDI in any downward direction if you were hit while you were in the ground, even if you SDIed Upward first.
Automatic Smash DI
Automatic Smash DI, many Melee players would be familiar with, is NOT IN THIS GAME.