Most of the RNG Events are triggered by the horniness of the girl. If you leave a girl alone long enough, she takes matters into her own hands. There are some story events that have randomness to them, but for the most part, the RNG events are just bonus events.
One, then the other. I normally start with Kate. Then sleep with them until Kate has sex with you. Then repeat with Lisa winning until she has sex with you at night. Then go to the bath room and talk to Kate about sex with Lisa. Finally, after all that, have the contest end in ties until they jump you.
Sex.
Go to her room at 1 AM for it. Keep it up until you can lose the condom.