After the dance finishes:

Once the music stops, but before you and your partner go your separate ways, a simple thanks to your partner is a must after dancing. This is not to thank your partner for doing you a favor by dancing with you, but to be polite. And while usually a “thank you” is responded to with a “you’re welcome,” the proper response to the thanks is also “thank you”.

Let your partner know if you enjoyed the dance and give them a genuine compliment. Find something specific to compliment if you can, such as a specific step that you enjoyed, or that you appreciated how well your partner led or followed. This is also a great opportunity to mention if you would like another dance later, but remember that dancing too many dances with the same partner, and reserving a specific dance ahead of time, are both violations of the unwritten social dancing rules.