Just make sure you are reinforcing the thing you want to reinforce! The dog's behaviour will tell you that. Also, things that are reinforcement for some dogs are not for others.
I am amused by one phrase in the article in Debra's last link. "I will go pet and kiss her if she is resting quietly on the couch". If your dog doesn't like hugs and kisses, they can actually be an aversive…...positive punishment.....like when you were a kid and that maiden aunt with bad breath insisted on "up close and personal". The dog will tell you that too. (My guy does not appreciate being kissed, but petting is O.K.)
If you are doing something that has been recommended and it isn't working, it's time to rethink and try a different approach. Not every dog responds in the same way to the same methods. I agree with Debra that many pups think someone squealing in response to their nips is wonderful and they respond the same way they do to a squeaky toy!