What you've been taught is a good general technique, but these are meant as guidelines, not rules, you should just experiment. Different things work for different shapes also.
I sometimes do the "darken socket line, colour lid lighter, highlight inner corner and underbrow" combo but other things I sometimes use:-
- Rather than darkening the whole socketline I just do the outer "V", this gives a softer look and works quite well with brighter colours as you're just adding a bit of definition/the suggestion of a creaseline without darkening much at all
- For some looks I use what I call a "sunrise" effect - I start with my darkest/strongest colour along the lash line, blending up across the lid, put a lighter/brighter colour on the crease, then use a lighter again colour up towards the brow.... so the colours are almost in "horizontal stripes" across the eye area fading darkest to lightest, if that makes sense..... for example I do a natural "daywear" look with brown on the lid (darkest at the lash line, sometimes I use wet shadow to line then smudge it up) and work sushi flower (soft peachy pink) along the socketline.
- Another shape I sometimes do which is very dramatic is black shadow (Carbon) under the eye, along the crease line and in both the outer AND inner "V"s of the eye.... then put a splash of bright colour on the lid (bright bronze or peacock green) in the black-outlined "window" this creates.... I call this my "Cleopatra" eye.
Hope this helps, Sho x