Wear the clothes that you will normally wear under the clothing you are measuring for. Have someone else do the measuring for you, as you won’t get correct measurements if you measure yourself. Take each measurement 3 times to ensure you have the correct ones. Have your shoes off when taking leg measurements, and measure to the floor for inside and outside leg measurements. For ¾ pants, measure an inside leg measurement to where you want the bottom of the leg to be.
All measurements should be taken with the tape measure relaxed, not pulled tight.