1. Look at a bunch of books and pick a good basic reference that you personally really like. I have the one you mentioned and I bought it because it was recommended. But the book I use all the time is Rotary Magic by Nancy Johnson-Sbero
http://www.nancyjohnsonsrebro.com/NJSBooks.html Go to the local library and borrow every quilting book you can get your hands on that looks even remotely interesting to you. I borrowed Rotary Magic hoping it would help improve my cutting. Turns out it covers everything to do with quilting and includes some beautiful patterns. I think it will always be my go-to reference. With so many fantastic online video tutorials, you might decide not to buy a so-called reference book at all. No rules.
2. On washing precuts: I wash everything including precuts. I used to fight the fraying until I read a great hint somewhere (?). DO NOT AGITATE. Simple. I wash precuts in the sink with a tiny amount of liquid detergent and a little splash of vinegar. Rinse well. Squeeze out the excess water......no wringing or twisting. Spin dry in my salad spinner (loved that hint) and chill until I'm ready to iron.
I'm just too scatterbrained to have somethings washed and some unwashed. I'm not very ambitious so I definitely would have gone the unwashed route, but some fabrics seem to make me itchy and sniffly, so I decided to go with washing.
3. I try not to be on one side or the other, but you might occasionally purposely choose one or the other if your pieces are a little too small or large. Sometimes seems to happen if you switch rulers for different shapes.
4. Press which ever way suits you best and gives you the best results. It a personal choice.
Most of all, as in the other posts, have fun. There really aren't any mistakes. You might do something that takes you in a direction other than the one you were planning to go, but hey, that's the creative thing, right?
Happy quilting!