The ideal tire pressure will be different for every rider, but in general, we want to run the lowest pressure we can, without risking flat tires from hitting potholes. A good starting point is to set the pressure so that the tires both squish down about a quarter to a half inch when you sit on the bike. The front will take less pressure than the rear.
Running your tire pressure this low allows the tire to deform over road irregularities instead of bouncing off of all of them. This means you get a smoother ride and you go faster/farther to boot.