Splebel
If you aren't using the Trampoline against shield, then start using the Trampoline against shield. At first it might look like you aren't getting much bang for your buck (7% for winning neutral), but the real purpose of the move is to condition your opponent into not shielding when they should be. They're going to be very wary of just sitting there in shield as you approach if they know that the Trampoline must be respected. Mixing up the trampoline, fairs/bairs/nairs, the hydrant, fruit, and even tomahawk grabs is the only way to get past the "my opponent is a brick wall" problem that Pac-Man often suffers from.
Also, being able to ALWAYS get the fair to key combo that's true from ~115 (rage, middleweight)/~130 (no rage, middleweight) to ~150 is absolutely essential, especially against reflector characters. You can't just throw your key out there and pray hit hits, unless you see that your opponent's options are limited or that they've committed to something. You've got to make them think you're going to grab or trampoline, hit them with the fair to key combo for the K.O., and end their career!
edit: and if your opponent is very good at catching fruit, try to get your fruit in hand.
melon: throw and run after it; catch it from an opponent's shield (risky if you don't pressure them); drop a hydrant, run off, and, a bit before you hit the ground, b-reverse it, jump up, and catch it; or jump off the stage, throw the melon at the wall underneath, and catch it that way.
cherry/strawberry: just throw and catch
apple: throw into a water gush coming your way, it'll drop on the ground and stay there.
bell/galaxian: fairly straightforward, practice these until you always get them perfectly.
key: practice catching on FD and Smashville. the timing is 1 bair, you can look this up. I hear it's also possible on the left side of Battlefield, don't have that down, though.
orange: same as key, I hear that it's sometimes possible to get it off the hydrant but I haven't been able to do this yet. (edit: possible, see
BSP
's post below!)