Directional Influence- A lot of people under-estimate DI. To solve that problem, we have XiF:
Basically, DI is influencing your flight pattern from an attack inflicted upon you, or any aerial movement. DI is most effective in escaping combo's, and surviving to higher percents. There are many types of DI, I'll go from the worst kind, to the best.
No DI: Just how it sounds, you dont influence your movement at all. Very bad for shine combo's, chaingrabs, staying alive, etc. In very rare cases it will be somewhat useful. Like, not DI'ing so you mind game your chain grabber. DI'ing outwards from characters like marth is bad too, cause it may set up for a tipper. Or even DI'ing may set you up for one depending. But in reality, you dont want to do this DI.
Simple control stick DI: before and during you get hit, you hold a direction and dont let go so you change your flight pattern. This is good for escaping some shine and chain grab combo's, and staying alive in general. But if you want to live to like 160%, this isn’t gonna cut it. There are other, better ways.
Double stick DI: this is extremely interesting, and it astounded me when I first saw it. You can actually DI with both the control stick and the c stick. You can pull off 2 different DI's at once, allowing you to greatly influence your flight trajectory. We were testing it with peach's forward throw. We were able to survive an f throw right near the right edge of Final Destination to about 196% and still live. One certain pair of directions made this (I think it was n up left, and left). But other ones made some pretty weird flight patterns. An up left on control stick and left down on the c stick caused the fox to actually go straight up from the up throw. Very... very interesting.
Anyway, I hope this kind of sheds light on those who kind of consider DI to be unimportant
Disjointed Hitbox- Every character has a hitbox for every attack. Like Mario’s forward smash will hit everybody in a certain area, or in his hitbox. When a hitbox is not attached to the character, such as in Marth/Roy/Link/Young Link's sword attacks and Ness's bat smash, its called a disjointed hitbox. A sword and a leg (such as Captain Falcon's) are going to be affected differently by fire. The character whose knee comes in contact with the fire is going to get hit, but the character with the sword is not, since damage to the weapon (a disjointed hitbox) does not affect the character.
Doctor Mario’s Up-B Cancel: Doctor Mario can actually cancel his Up-B. After you press Up B (Up and to the Right preferably), to cancel it, quickly tap in the opposite control stick direction. If you succeed it will be very noticeable, just keep practicing because this is one of those things that will take time to master. Credit to AlphaZealot from SWF
Double dash attack- Requires a super scope, ray gun, or fire flower, as these items do not have a running attack. Do a dash attack holding one of the items, and while you're doing the attack, hit Z. Your character will attack, then throw the item.
Double Jump cancel- Basically, you can stop the upward motion of Mewtwo, Ness, Peach, or Yoshi's second jump with an aerial attack. For example, if Ness does two jumps in short succession, followed by a quick aerial attack, he should be VERY low to the ground. This is useful for combos and mind games. Double Jump cancel is abbreviated "DJC."
Edge-guarding- Attacking the enemy as he/she is trying to get back onto the stage. This technique is NOT cheap, it is how the game is played.
Edge-hogging- Only one character at a time can hold onto an edge. So if you are on the edge, your opponent can’t be. This is useful in preventing an enemy's recovery. The best way to edge-hog is to either wavedash or short-jump backwards onto the ledge.