How do I teach a puppy not to pee on the floor?

Especially when she meets new people or when she thinks she’s in trouble(even if she is not). We’ve put her nose in the pool of pee a few times when we caught her in the act and spanked her a little. But I don’t think that’s getting the point across or helping much, just scaring her. She seems to be a pretty smart dog, just a little shy and not very brave.