The range that you wanna stay in is more or less the range where Falcon's nair will hit with the tip of the toes. Falco will use his movement and lasers to keep you out of this range. Get good at powershielding lasers! You will need a combination of powershields, wavedash OOS, jumps, wavelands full hop aerials and nair oos to get into this range. Practicing powershielding lasers against lvl 9 Falco on FD is a pretty good exercise and I higly recommend using trigger trick (described below). Once you get into this range your nair outspaces Falco's aerials, and he can't safely short hop laser. A thing about Falcon that you must understand is that he is more or less an anti-air character. You wanna try and catch your opponent in the air with a nair or uair. At low pct this will almost lead into a grab on fast fallers! If you catch a floaty in the air with a nair this usually leads into more aerials/death. Falco has alot of moves that will lead into a huge combo against Falcon. Within this magic range you have to constantly look out for nairs and dairs! If you're at a pct, where CCing Falco's dash attack is no longer possible, be careful of this as well. Shield grabbing early aerials is one option. Stomp out of shield usually works on early aerials too, as long as they don't utilt after. The best option though, is to dodge them and be ready to grab!
Whenever Falco has his back turned to you, you need to be looking out for utilts and bairs. Bait these out and grab! Whiff punishing utilt can be quite tricky, but shield grabbing it is a walk in the park. In a situation where Falco has his back towards me, I like to run in and shield just as he utilts. Then I grab him and throw him on the grooouuund!
Every nair you do should be spaced so only the tip of Falcon's toes hit him. A properly spaced nair like this beats just about everything Falco can come up with, it even goes through utilts alot of the time. Again, hitting him while he's airborne will lead to either a grab or a knockdown depending on pct, but if Falce is grounded, he will CC or shield the nair. This is another reason why we only touch him with the toes. If he shines or dtilts out of his CC, it won't hit you due to your godlike spacing. You will have to beware of fsmash after CC though. It has enough range to get you despite the spacing. I usually shield after a spaced nair in case of this and start taking mental notes. If I notice he likes to shine or dtilt in this situation, then I just knee or stomp him in the face. If he fsmashes, I shieldgrab it. If he tries to CC grab/shield grab the nair, the grab won't connect due to the aforementioned godlike spacing, so again just knee him in the face as he tries to grab. Another common response to the nair is to roll or spotdodge. Punish these habits! Falco knows that Falcon's grab is devestating. A lot of Falcos spotdodge to avoid the grab. Mindgame them into thinking you're going for a grab and just knee/stomp them instead. A safer alternative is to DD and grab after the spotdodge. Another spaced nair also works wonders and is a very safe option.
Whenever your land a poorly spaced nair, get a jab out as soon as possible. Don't get predictable with the jabs. Sometimes gentleman, sometimes one or two jabs, sometimes rapid jabs too. Nair to gentleman on shield isn't guaranteed shield pressure, but if you land your nair as low as possible on their shield and jab as soon as you are able, it's pretty damn tight.
When Falco is in the air, or on a platform, don't be stupid and stand under them in such a manner that they can hit you on their way down. Dumb Falcos like to throw out dairs as they land. Dodge and punish! Another key thing in this match-up is to get your OOS game tight. Know when to stomp, nair, bair, uair, roll, wavedash, shieldgrab and shield drop. Look out for cross-ups too. If you think they're going for a cross-up, just turn your back to them, shield, and grab them as they land on the other side in front of you.
When he's off stage you wanna try and snipe his side-b or doublejump with a soft knee. Most of the time it will combo into an upair. Jumping out there can be scary, but the only way to learn it is to practice! That's what friendlies are for!
These are a just a few things I can think of off the top of my head. A better player might be able to give you better tips, but what I've written should get you going in the right direction. Also I talk alot about nairs in this text, but don't neglect the occasional uairs, knees, stomps and bairs. Using nothing but nair will make you very predictable. If you need more advice I'll be happy to help you as good as I can. Either PM or reply in this thread.