I learned from the internet and very little from books. Just experiment and make swatches of different stitches to compare with. You eventually get the idea of how stitches will look when you crochet enough. Some people have to use patterns a bunch to understand + have it stick and some can do it by looking at a picture (me xD).
Probably. I'm printing out patterns and saving it for a binder (dividers!!) .. also including the url/name in it too. Just in case. I've always had those moments when you think you don't need something, but later you do.
And I just think it's a good idea to save your favorite patterns because you never know how long it will be available online. You might not be able to search for it easily or the website might go down or be unavailable.