Good for you! I think it is just so important that horse owners educate themselves well on this topic. Being a HCP specialising in rehab, IMO most 'acute' problems come about because the more minor(but often chronic) problems are unrecognised or ignorred.
IMO 'what should a properly trimmed hoof look like' is the real question - shouldn't be fundamentally different to a shod one. But as others have mentioned, the specifics are individual & it depends. Altho the *principles* that govern what/how you do it are pretty well uniform, so that's the most important thing to understand IMO. It also depends what a hoof is like before the trim as to what it 'should' look like after. Eg. a well trimmed, healthy, high performance bare foot will look vastly different from a well trimmed foundered foot.
hoofrehab.com & barehoofcare.com are another 2 great & well researched sites with heaps of info & links to other good sites & references.