- Light Shield -
Light shielding is an extremely important option to consider when fighting a Falco. Typically Falco will approach with SHL -> shffl'd d-air -> JC shine -> some sort of full hopped aerial. These are the easy Falcos. You can just hold your hard shield up against the shine rather than going for a grab, wait for the to jump, and follow with an up air. It's when the Falco's constantly shuffle d-airs -> JC shines that IC have a problem. With a hard shield up, you'll find yourself getting locked up and make a dumb decision.
This is where light shielding is important. If you get hit with the d-air while light shielding, you'll slide back. This does 2 very important things. It distances you away from the shine allowing you to make a better decision, and it can mess up a lot of l-cancel. Both of these allow you to react favorably. Jab -> grab, dash attack are good offensive choices. U-tilt and f-smash are good defensive choices.
Light Shielding also deals with Falco's down throw. I know what your thinking, "ICs worrying about Falco's throws? Boulder dash!" Well unfortunately, d-throw messes up ICs pretty well, if Falco can grab Popo that is. The hitbox from the laser stuns Nana so she can't rescue you with a d-smash or jab. If you light shield correctly though, Nana's shield will be larger than Popo's (not sure if this is the reason) and Falco grabs Nana rather than Popo. All you have to do is keep shielding until he throws, then punish.
- Edge Guarding -
Every time you knock Falco of the ledge do your best to make sure he dies. A good Falco is way too dangerous to let back on the stage, regardless of his damage. Luckily edge guarding Falco isn't all that difficult. First thing you want to do is judge where Falco's going to be recovering from.
From Below:
When Falco's below you, he's has 2 options. Sweet spotting the ledge or overshooting it. Of course pretty much every Falco is going to opt to sweet spot so here's what you do. Instead of charging a d-smash that can be teched or missed, you should do a ledge hopped d-air. This way even if he decides to overshoot the ledge, you'll connect with the d-air and send the Falco into panic. After they panic, most Falco's will try to up B as fast as they can, making sweet spotting near impossible. Here's where you go for the d-smash. Try and space as well as possible and connect d-smash after they've passed the ledge, so they'll miss the tech.
Even to the ledge:
Not a lot to say here, he can phantasm or firebird. Most the time he'll be to far to firebird back on to the stage though. Pretty much all you need to do is ledge hog and roll. Dead. If he close enough firebird onto the stage, he's also close enough to eat a ledge hopped b-air. This usually finishes him off or sends him to the recovering from below option.
From Above:
Here's the trickiest Falco to edge guard. He can phantasm/firebird above you or firebird to sweet spot the ledge. Don't bother to try and interrupt his phantasm, just follow him up with a d-smash or grab. When he goes for the fire bird is when it gets fun. Falco can go for the ledge, go above you, or go at you. A whole bunch of options open up for you now. You can try and guess: either charging a smash or go for an up/b-air. Problem is half the time you're going to be wrong. I found two good alternatives. The first one is go back to the ledge hog idea. Then ledge hop an u-air, hopefully you'll connect and it could lead to a b-air. The other more creative (unfortunately less practical) method is to desynch Nana to charge a f-smash and have Popo go for an u-air. You should be able to get it off right on time if you side step desynch right as you see Falco start his firebird. The button combination is a little tricky at first (Dodge, smash and hold A, tap X/Y while holding A, release A and tap it again for the aerial attack.)
- Dealing with Lasers Approaches -
Make sure to jump and fire ice blocks to give yourself some room to work with. Falco has to deal with them. He can full hop, shield, shine, roll, or just take the hit. No matter what choice he goes with it stops the lasers stop for a little bit. The first thing you want to do is get closer to Falco, so in this down time wavedash in. If you're already relatively close you can punish his decisions. Full hop is punished with u-air -> b-air; shielding leads to grabs (watch out for side steps); if he shines go for a f-air; and if he rolls use a dash attack -> **** (grab/smash/u-air.)
If you feel that Falco is getting to close, a lot of the time you can get away with rolling away from him and desynching a blizzard. Alot of the time they'll try to f-smash or d-air and eat the blizzard, in which case you get a nice grab. Be careful to not roll behind Falco. He can f-smash you faster than you can throw out a blizzard. Rolling away with a desynched blizzard is also a great way to start off one of Falco's stocks. When you roll you seem vulnerable, and they rush to punish you, only to be met with a blizzard.
The key thing to remember here is don't let him camp you. If he's firing lasers at a distance make sure to send ice blocks his way so you can get closer. If you sit on the other side of the map waiting for him to come to you, he'll just shoot lasers all day long. On top of that IC are to agile in the air, as far as approaches go, so this rules out pretty steadily.
- Last Note -
It's always going to feel like Falco's exerting the pressure in this match until you either get him in a grab or start a combo. Don't worry about it too much. Falco player's are scared sh*tless of your grabs and smashes. Just be patient as wait for your opening.
Hope this helps out.