Check your phone ingame. But assuming you're going the corruption route, just focus keep meeting girls and choosing the red options. Use your phone to buy condoms and give them as gifts once a day. To make money, go to the tanning parlor and work for Frank from 10AM to 8PM when you don't have anything better to do. Go on dates on the weekend.
To become a gang member, first meet Bruce and Davide at 8 PM on the porch, then at 9 agree to do some drug deliveries. Once you've done that twice and spoken to them again, you're a gang member and can enter the basement.
Don't skip the scene with Nicole, Davide and Bruce at 10 PM or the game doesn't register your progress properly. Once Nicole's corruption is high enough you can take her there and drug her, the next day she'll be sick. That night, go into the basement again and don't drug her, then on the weekend you have the second date opened. After the second date, you can take her into the basement again to make her yours.
For Cassandra, just keep meeting her in the kitchen at 9AM and taking her into the basement after you've raised her corruption. Eventually you get the option to have sex with her, after which you can take her into the basement at 10PM if you've already made Nicole yours.
Alexis's path isn't as far along as the other two.
