How to tell apart those "brown birds"?

Nature Talk
2

My hardcore nature enthusiasm got started by connecting as a child with Audubon, but I have since reverted to herps and am not an expert with birds. That said what helped my ID skills, first with birds then with herps, is just to make yourself familiar with pictures (and for birds calls too) that you know are correctly IDed, like websites and guides. Also use iNat to see how other people ID, and start (or continue) IDing yourself and see what people say when they correct you. To answer your other question, any of the Peterson line of field guides is great. I think Peterson has an Eastern and Western volume on birds.