When the Prophet (Sallal laho alaihe wa aalehi wasallam) came back from Meraj he called Sayyedina Bilal (Radi Allah o anha) and asked him "what ibadet do you do extra?" He replied "Ya Rasulullah (Sallal laho alaihe wa aalehi wasallam) I don’t do any extra ibadet except that I always do 2 rakat nafal after every wudu”. The Prophet (Sallal laho alaihe wa aalehi wasallam) said I heard the sound of your footsteps in front of me in Jannah (paradise).

Hadis Kudsi:

Allah says anyone who was without wudu and he did not do wudu he did jafa (disloyalty) with Me. And anyone who was without wudu and he did wudu and did not do 2 rakat Tahayyatul 

wudu Salah he did disloyalty with Me. And anyone who was without wudu and he did wudu and did 2 rakat Tahayyatul wudu salah and he asked a question from Me and I did not give him what he asked for, then I would be a zalim (cruel). But your Allah is not zalim (cruel).

Method of doing this Salah

Just read 2 rakat salah after every wudu and read any surah in it. Then after salam do a dua.