To measure your bust – Measure around the fullest part of your bust with a bra on, as you will be most likely wearing a bra under your new clothes. So around the back and over the fullest part of your bust in a horizontal fashion.
To work out your waist size – Measure the narrowest part of your torso firmly with a tape measure. Your natural waist might be a lot higher than you imagine and should be a few inches smaller than your jean size. Your narrowest part will often be just below the ribcage and above the belly-button.
Measuring your hips – Can often be the most tricky part as with vintage measurements the hip is not the hip bone but the fullest and widest part of your behind. It may be the measurement around the middle of your bottom or slightly further towards your thighs depending on your body type. Just make sure it is the widest part.
If you're tall or petite it is also a great idea to measure the length of a garment you already own if you struggle with getting items to fit when it comes to length.