For some reason, I was doing bail missions but when I was done with them, I don't know what to do. I have no main story missions, or Strangers and Freaks missions for Trevor. I did the bail missions after Mr. Phillips on my PS3. What shall I do?
According to this page, finishing Mr. Philips should unlock the two next missions: Nervous Ron and Trevor Philips Industries, given respectively by Ron and Tao Cheng. So except if you're experiencing a bug blocking the following missions, you should already have access to these two.
If this is the exact point where you're stuck, maybe do you have a save file right before the first Trevor appearance? If you do, try to load it and replay the missions to see if something is triggered this time.