Okay, I'm not an MK main, but I think I know a few things.
Don't use Drill Rush
Use more aerials
Don't Drill Rush suicide
Use your multiple jumps
Don't tornado past short hop height above a landing platform.
Use your tilts.
Don't be afraid to Gimp.
Don't be predictable.
Pressure... a lot.
Space well.
Use your glide-attack before you hit the floor so it doesn't have as much landing lag
Don't spam D-smash... 3 times in a row... with your opponent that has a counter right in front of you.
Use your 5 jumps to recover and gimp instead of simply using Up-B and falling to try and grab the ledge.
Use N-air and D-air to help gimp.
Use U-air.
And don't try to grab so much... especially if your opponent is 1/3 of FD away.
Nice ending
Oh, and I'm pretty sure this is a rule for all boards, read the stickies.