While performing ablution, the Prophet (peace be upon him) would do some acts that have been classified later by scholars as supererogatory acts. That is to say if one does them, one takes a reward because of following the Sunnah of the Prophet and if one neglects them, the ablution is still valid and one is not punished.
In this video, Sheikh Yasir Qadhi talks about some of these acts, such as Istinshaq (sniffing water and blowing it out), Madmadah (rinsing the mouth), etc. In addition to that, he sheds some light on the healthy benefits of keeping on these acts of Sunnah.