What's the current treatment recommendations for warts? Years ago I had one burned off in my doctors office with liquid nitrogen I think it was, but I could be wrong. My mother's doctor when she was young walloped one she had on her hand with a heavy Bible! I'm not joking, that really happened.

Since it's been many years since I've had to treat one on my hand I thought I'd ask what's the options nowadays? And what can cause them to appear anyway?