1) Honestly, just practice - Unless your controller really does have serious issues, then I'd suggest just replacing it. I've been only doing it for a bit but it doesn't seem like anything too difficult to handle.
2) You and your opponent have objectives. Investigate what objectives they are and find out ways to either accomplish YOUR objective, or deny your opponent from accomplishing his/her's.
The most obvious example is in the Falco vs Marth matchup. You want to ideally shoot safe, low lasers (can't be PS'd) and zone marth until he's at a position where his options are limited. From there, you'd attack him. Marth wants to catch you doing a bad laser or standing in the range of his grab/down-tilt. The most obvious thing that comes into mind in this matchup is being able to constantly adjust your space so that you can move in and out of his 'threatening' range. Learn how to navigate through space using dashes, hops, wavedashes, and more. Learn how to control your use of laser to achieve different objectives - Because setting up laser -> aerial isn't the only way to go. Learn how to bair and dair in retaliation to careless approaches. Learn how to attack Marth when he's trapped next to the corner.
3) This is too vague of a question, but it relates back to my previous paragraph. Discover your opponent's objectives and their 'threatening' range and manipulate your character around it.
4) Openings generally exist when you either reduce your opponent's options or have a psychological tact that can be manipulated. Are they always afraid of getting cornered and tech roll to the center? What about rolling to the center? Do they always nair oos in retaliation for a laser approach? You have to be constantly on alert to these kinds of things.
Dash dancing is for space readjustment. Please refer to my previous paragraphs to see why you need to do this. There's also feinting, creating more psychological shafts to manipulate, and other stuff. PP really puts it nicely when he subdivided M2K and Mango's playstyle back in the documentary - There are players who look to exploit the system mechanics of the game as much as possible, and those that exploit manipulating their opponents as much as possible.
One of the biggest tips I'd give to beginners (myself included) is that you don't constantly have to be doing an action or attack. Propelling yourself to better positions and waiting for your opponent's pre-emptive actions as a result of your previous ones (aka letting them hang themselves) is much better.
Falco's a marvelous character whose defense really is underrated. Make use of everything in his tool-kit to unleash utter destruction on your opponents - He's a really great bully.
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Random, but is anybody really consistently with dair xx shine -> dair xx shine vs Marth on FD?
I swear, I'm never able to complete the second shine because my dair always ends up hitting too high. If I delay it to hitting low and then fast fall, Marth just spot dodges away (20XX hack pack). I'm definitely doing this wrong and aren't sure how to correct this. I know it requires specific DI, but even with that, I still miss it.
Video example to show what I mean:
Mango does nair xx shine -> dair xx shine, but its more or less the same thing.
