How to get information that a bad player has a good hand?

Anyone have advice on when to pick up on a bad player that gets a monster hand?

I usually separate bad players into two categories: Bad preflop players and bad postflop players.

Sometimes players will go all in only with huge pairs preflop but they will make big mistakes after the flop and call with not much of a hand...Other times players will start shoving all in with any two cards before the flop yet they will tighten up after the flop.

I am going to assume this is for online play. The only thing you can focus on with online players are betting patterns. A donk will always be a donk, so a great majority of their all-ins pre or post flop are bad. I would though be more weary of post flop.