Hard reads are useful, or use it against people like Cloud, Ike and Little Mac who can't snap to ledge, that's what I use counter for most, also active hit box recoveries, Roy, Corrin and Link are examples of characters it's good against, it also decimates Ness when he tries to recover, or if your opponent has commited to a slow move at a bad time, IE Bowser dedicating to an f smash with no set up, or warlock/falcon punch, apart from that, it can be good against predicatble players, be careful though since they might change their habits, the last use I can think of is on neutral get up, but that's very punishable, so use it scarcely, just never use it randomly, or when recovering, and it can punish charge moves if your opponents keeps charging you can force them to hit the counter, but never counter while someone starts charging, 'cause they'll punish you for it.