What is the minimum and maximum number of rak'ahs for Qiyam al-Layl, and what is the best time to perform it?

The night prayer (Salat al-Layl) is a confirmed supererogatory prayer (nafilah mu'akkadah). Its minimum is one rak'ah, which is the Witr prayer, and its maximum is eleven rak'ahs, which is the reported Sunnah. It is permissible to add more, based on the general statement of the Prophet (peace be upon him): "The night prayer is two by two," and due to the practice of the Companions. The best time for it is the last third of the night, to coincide with the Divine Descent. For one who fears not waking up, it is better to pray and perform Witr before sleeping.