Hi! Welcome to the land of Digi!
1) I organize by Designer/kit. Meaning, each Designer has her own folder, then each kit I buy has it's own folder underneath. I use ACDSee to organize my stash, so I do not break up alphas or elements from the original folder they came in. ACDSee allows me to add tags based on the way I look for stuff to scrap with. This is a whole separate topic of discussion LOL!
2) I scrap at 12x12 and print at home 12x12. I really like that format the best for my personal albums. When I'm reprinting LO's for grandparents, etc., then I resize and print at 8x8.
3) When I first started out about 4 years ago, I used the tutorials on Scrapbook-Bytes. Misto Cato (one of the designers here) has some excellent tutorials on her blog.
Good luck and have fun!