12. measure your inseam

Start at the point where your leg meets your torso. It is in the middle, where the crotch seam and inseam would meet when wearing tight jeans f.ex. From that point go down along the inside of your leg, where 

generally the inseam would lie, go across your knee down to the middle of the ankle bone. 

If you are alone, start at the crotch seam, hold the tape measure at knee height and then continue measuring down your lower leg. This will allow you to read the 

correct measure at the middle of the ankle bone.