We (usually) use the old FAA rules, so over 8 flight hours three pilots, and over 12 flight hours four pilots. We are contractually limited to a max 20 hour duty day (duty day starts 1.5 hours prior to scheduled block, and ends 0.5 hours after block in), extendable to 22 hours max. If we have a deadhead at the end of the "day", then we are limited to a 20 hour duty day, unless we are going home...then WE can waive the 20 hour limitation...
Our min rest is 12 hours block to block, and we frequently have 24 hours rest. If we know we will not have the rest time we need before the flight, we can call scheduling and tell them to delay our wakeup call to whatever time we want. If we are fatigued, including at the time of the wakeup call, we call fatigued, and automatically get 12 hours crew rest...they ask us if we need more time.