If the dryer shows no signs of life (the digital display is dead or the drum light doesn't turn on when you open the door on a dryer with a dial timer), check the house circuit breaker and reset it if tripped. For a gas dryer, you can test the outlet by plugging a night light or small appliance into it.
If the dryer's electrical outlet works, then a bad power cord, failed timer or faulty electronic control board can prevent the dryer from working. These videos can help you figure out how to fix your dryer when it's completely dead.