Eh. Oh how I love Falco.
You actually have the advantage. There's a couple things you can do:
~ Power Shielding: People already said it, but didn't explain it (assuming you don't know of course). Shield right when one of his lasers (and most Falcos use them for their approach) is about to hit you. There's like a 6 frame window (I think?) to when your shield goes up to reflect their laser.
~ Grabs: Marth loves fast fallers. Up throw works the best, but if you feel pretty ballsy enough, you can try tech-chasing them (chasing them after they tech and follow up with an attack or grab).
~ Watch your spacing: Like the guy above said, if you're letting him crouch cancel him out, you need to work on your tipper spacing so you put knockback onto him. Once you get him moving on your terms though, you're in control, and from there, follow through with combos.
~ Mind Games: These are important in every game. Personally, I like to Dash Dance once left then right, wavedash back, then let him follow through so I can hit with a tipper, Nair, or Fair.
Blah. There goes 12 minutes of my life. ;/