Posture is more than just how you look -- it affects your brain. Too many of us suffer from posture problems, so here's a guide that helps you identify what kind of problem you have, and what you can do about it.
The guide was created by a Redditor who came across an article on BodyBuilding that talked about fixing your body's alignment. The freely downloadable spreadsheet shows, with illustrations, what your posture problem is likely to be. Once you've identified that, look at the information on what muscles are strained or underactive, which workouts you can do to fix this, and which stretches you should be doing.
The second sheet of the spreadsheet explains each of the stretches mentioned, with images, so you don't have to go hunting for them. The images aren't loading for the first few stretches, so you can google those, but the descriptions are pretty simple to follow regardless.