Wash the jeans in hot water
Dry them on the highest heat setting
Repeat the wash-and-dry cycle if needed
Soak the jeans in hot water for 20 to 30 minutes before washing
Use a dryer after the hot soak to tighten the fibers further
Turn the jeans inside out before washing and drying
Check the fit after each cycle to avoid over-shrinking
Avoid cold water and air drying if you want maximum shrinkage