Flaws in images:
If it's a portrait look for background things that seem to protrude from the head like a pole or a tree branch
In landscapes look for the horizon line being tilted or simply a static shot that has no real interest or story - sometimes a close crop can change the drama significantly
Look for careless attention to composition - cluttered photos, subject is too centered (boring photo) Interesting photos follow the rule of thirds
Bad photos will include whites that are blown out, poor focus and that "snap shot" look to them. Often noise (grainy look) will take away from a photo's quality, however noise can be used to add to a photo's quality in that it adds an aged quality for nostalgia.
I won't offer links, you'll have to do that - Do keep in mind that photographers are very protective of their work and often the image is copyrighted - have the courtesy to ask permission from the photographer, their page will probably have a link for email. I bet most would be happy to contribute to your learning.
