Some things I like
If a Sheik is Up-B stalling, light shield edge hog her.
When edge guarding a Marth coming from below, stand up on the ledge so you avoid the up-b, and shine. Also stand up vs Sheik at the point where if she goes for the ledge, she'll et edge hogged, and if she goes up, just WD back onto the ledge. If she lands on the stage, grab, uthrow, uair, or usmash at a percent it will kill.
If you're player 2 or 3, if you re-spawn on Battlefield, hold a direction and aerial, and stick with that direction, and you'll edge cancel on either side of the platform. On the grass for of Stadium, when you re-spawn, do and aerial and hold right and you'll automatically edge cancel on the wood platform. Etc...
Tough technique: Instant wall jump (on FD), laser towards the stage, then sweetspot the ledge with your up-b so you renew your wall jump, and repeat. Being able to renew the instant wall jump is the hard part.
Bair to grab works wonder on characters like Peach and Marth at lower percents.
WD off the ledge, fast fall past the ledge and jump<bair, is really good for edge guarding. Best in cases such as a Mario shooting a fireball, this way you sneak under it and get the KO. Coming from further away, shine turn around and fall past the ledge and jump<bair is good. It catches them off guard.
Dash at someone when they are shielding, then shield right in front of them, but then jump out of it when you still have enough momentum to get behind them. They may try to grab you, and get baird.
Wall jump air dodge is a good way to recover, compared to Up-B in that situation.
A fun thing to do on Fast fallers at very low percent, is uthrow, and if they don't Di, step to the side a bit, and let them land, If they don't Di, they expect to get hit, so they most likely won't tech. Once they've landed, jab them. They'll be forced to stand no matter what. Then fall on them with a uair, then usmash, or grab after that. It works on really good players, I've tried it.
On a Fox or Falco, near the edge, forward throw, then wait a second. Then run off, fast fall, and jump back up with a nair. they usually Side-B into it, then you can shine them.
Do a rising dair to edge guard Falco and Fox's up-b. Falco will just get edge hogged after it, and you can just shine Fox, or repeat. They can't DI it onto the stage if done right.
Use a nair from the ledge to edge guard illusions. It stays out there longer than a bair would, and the hitbox makes it easier to knock them the way they came from. Works with all sex kicks, a lot of players do it with characters like Samus, Link, etc.