Individual banks change their lending and deposit rates at their own discretion. The only thing that's consistent is that most everyone raises/lowers their prime rate on the day that the Fed announces it is raising/lowering the fed funds rate, which only effects you if your loan or deposit is indexed to prime.
The Fed rate changes are announced on Tuesday FOMC meeting days at around 14:00-14:15 ET. It's usually broadcast live on CNBC, and should appear immediately on most financial news sites/wires. You can see the calendar at http://www.federalreserve.gov/fomc/ .