If you want to end a conversation and then, all of a sudden, start stuttering because you don't know how to appropriately say goodbye in English, it can be very awkward. To prevent this from happening, you will find here some helpful phrases.
As you use polite phrases like "Nice to meet you" when you greet someone, you should not forget similar phrases when you say goodbye to someone. There are several possibilities: you can either wait for what your dialogue partner says and then reply the same or choose your own polite goodbye phrase.
You might also be interested in the article Greeting someone.