Blown head gaskets are not inevitable, it's not uncommon for example to see PSA diesel engines with nearly 1,000,000 (yes a million) miles on the original gasket.
Signs of a head gasket are:
Overheating
Water pressurising and blowing water out of the header tank
Oil in the Water
Cold heater
Loss of water
Pressurised water pipes (usually with other symptoms though)
White smoke (actually steam) from the exhaust
Things that can cause a head gasket failure:
Bad design (some engines just suffer from head gasket problems such as the Rover 1.4 petrol engine or the PSA 1.1/1.4 petrol aluminium block engines.
Warped cylinder head
Warped block
Incorrect fitment
Weak or faulty water pump causing the engine to run too hot
Faulty thermostat causing the engine to run too hot