out of the factory tire pressures for the 325i are:
front: 29 psi
rear: 32 psi
(as fletch said already.)
with 5 passengers + luggage, the specs (factory) are:
if you are using the trailor hitch then increase the rear tires by 3psi.
note that changing your suspension, tire size, and vehicle weight can all affect the recommended PSI.
Also note that (bmw?) PSI numbers are given and recommended at 10 degree (celcius) weather (18`F). Tire PSI can fluctuate by +/- 4 PSI in extreme cold, or warm, temperatures. So adjust your PSI accordingly depending on the current weather conditions.