I say focus on how the opposing character seems to go about searching for grabs.
In the Falco dittos, the number one way I swear is simply jab -> grab, spot dodge -> grab, roll -> grab attempts. In these cases, rolling can be avoided by simply making sure you maintain your spacing and train yourself to punish rolls when you see it not being surprised.
Against spot dodges its more of a gamble, seeing how the first jab works and following up with double jab or even rapid jab to wait out the spotdodge seems best. Against another Falco's jab, jabbing right back I feel is the best solution unless you roll right away.
For characters like ICs, Wario, and Pikachu, I am not as certain. Wario seems to rely upon linking his moves like Fair or Dair into a grab. This or attempt to air dodge behind you. So, making sure you DI properly any attacks or maintain your spacing to avoid being hit.
Against ICs, I think the best counter to being grabbed is to grab right back and avoid shielding as much as possible. Unless the ICs are trying for a set-up with Ice Block or Squall or Blizzard, then it seems they are going for shield -> grab set-ups. So, trying to attack a shield might lead to it being powershielded or too laggy they can grab you anyway. So, I say call their shield approach and just grab. Not sure if you could get port priority on port 4 to avoid being attacked when throwing?
Oh, and I suppose the other option is to camp platforms, but I only see this being viable in the Falco ditto as CG from Wario and Pikachu are active on your stock for much longer. Although, I think Pikachu loses its ability to CG at 60%.