Coolant change/flush

What is the proper procedure to drain/flush/change the coolant and how often? I hear the dexcool will not last the 5 year/160000KM as stated. Any help would be appreciated.

Thanks,

Mark

The word I'm hearing is that cooling systems with DexCool should be flushed every 2 years/30,000 miles. That is the reccomendation I am now following, and at the time of the flush/refill I am replacing the thermostat and radiator cap just to be on the safe side.