tbh i think it just comes down to three things altho this just might be me being bad at giving advice!!!!
1) don’t be afraid to draw ugly people, if youre drawing all your characters based on faces you think are attractive then you aint gonna get far
2) try to think more in terms of caricature than representation!! push those features as far as theyll go
3) facial features never matter as much as facial structure imo. i always see pages of people drawing different noses/eyes/mouths/whatever for ppl to use for characters, and cool i guess, but if you really want unique characters, what really matters is that your characters have unique facial structures (altho a solid character design should have a combo of unique features and structure ofc)!!! for example, you would probably not mistake these characters for each other
but you could pretty easily mistake these characters for each other
unique hairstyles also help a toonnn in differentiating characters. tldr; givin them each their own individual silhouette should be your first priority if you’re shootin for unique characters!!! also doing studies of peoples faces is Good
We Are What We Feel 