How to increase the chance of an expensive skin?

How to increase the chances of getting an expensive skin when opening cases? Surely many of you have faced the fact that you open a case, hoping to get something valuable, but in the end you get a skin that does not even pay off the cost of the case itself. Some say that everything depends solely on luck, while others are sure that there are certain ways to increase the chances of an expensive drop. Perhaps you should open cases at certain times of the day or use some tactics?