As far as the methods of choosing concubines for emperors are concerned, I think there should be roughly three kinds. 1 should be the way to roll the dice. Because the emperor didn't know who to choose as the person to sleep at night, they could let the concubines sleep with the dice-throwing person.
The second method should be to rely on the eunuch to flop. The eunuch can bring a big silver plate with the names of all the concubines written on it, and then the eunuch starts to turn over which concubine is turned over, that is, the concubine. Personally, I think this can be operated behind closed doors. If a concubine bribed the eunuch, the eunuch might deliberately turn to her, and she would have a chance to be with the emperor.
The last one, I think, should be the emperor's own choice. If the emperor happened to love a concubine at that time, he would always want to be with that concubine. The last way depends on the emperor's own preferences. He can sleep with whoever he wants.
The above three words are probably the rules for the emperor to choose concubines to sleep. Therefore, according to these rules, it is very difficult for many concubines to see the emperor, let alone spend the night with him. Therefore, their lives are still very miserable.