Measure through the arms and round the fullest part of the chest.
Measure around the natural waistline, taking care not to pull it too tightly.
Measure with shoes on from the crotch to the desired length.
Measure from the natural waistline to the knee.
Measure around the base of the neck where the collar usually sits, taking care not to pull the tape too tightly as it is important to have a little extra room around the neck.