I would definitely watch at night the prayer observed by the Messenger of Allah ﷺ. He prayed two short rak'ahs, then two long, long, long rak'ahs, then he prayed two rak'ahs which were shorter than the two preceding rak'ahs, then he prayed two rak'ahs which were shorter than the two preceding, then he prayed two rak'ahs which were shorter than the two preceding, then observed a single one (Witr), making a total of thirteen rak'ahs (Using translation from Muslim 765)  

أَنَّهُ قَالَ لَأَرْمُقَنَّ صَلَاةَ رَسُولِ اللهِ ﷺ «فَصَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ ثُمَّ صَلَّى رَكْعَتَيْنِ طَوِيلَتَيْنِ طَوِيلَتَيْنِ طَوِيلَتَيْنِ ثُمَّ صَلَّى رَكْعَتَيْنِ وَهُمَا دُونَ اللَّتَيْنِ قَبْلَهُمَا ثُمَّ صَلَّى رَكْعَتَيْنِ وَهُمَا دُونَ اللَّتَيْنِ قَبْلَهُمَا ثُمَّ صَلَّى رَكْعَتَيْنِ وَهُمَا دُونَ اللَّتَيْنِ قَبْلَهُمَا ثُمَّ صَلَّى رَكْعَتَيْنِ وَهُمَا دُونَ اللَّتَيْنِ قَبْلَهُمَا ثُمَّ أَوْتَرَ فَذَلِكَ ثَلَاثُ عَشْرَةِ رَكْعَةً»