It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that when the Prophet (peace and blessings be upon him) woke up at night, he would use the tooth-stick (miswak), then perform ablution and recite this verse: "Indeed, in the alternation of the night and the day" [Surah Yunus: 6] to the end of the two verses. Then he would stand and pray two units (rak'ahs), then lie down and sleep until the sound of his breathing could be heard in his sleep. Then he would stand and pray as before, then come to his bed, then stand and pray two units, then do as he had done the first time, then pray the Witr with three units.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10607