Most size charts are very basic with bust, waist, and hip measurements.
Get out that tape measure. If you don't have one you can purchase one even at the grocery store in the sewing section.
When taking your bust measurement you are measuring the largest part of your bust. Bring the tape measure around your back and around the biggest part of your bust not holding it too tight or too loose. Taking a couple of deep breaths and seeing where it lies is a good idea.
Taking the waist measurement is very confusing for people. What you should be measuring is the smallest part of your waist. Look in the mirror to make sure it is the smallest part of your waist you are measuring. It varies for everyone. If you are looking for swim bottoms and you know your natural waist falls very high, you will want to choose a slightly larger size for around the belly button area. That way you will bet a better fit with your swim bottoms.
Finally, taking your hip measurement is not around your hip- bones like a lot of people think. It is actually the biggest part of your bum. Using a mirror for this measurement is advised to make sure the tape measure is even all the way around.
There you have taking your measurements in a nutshell.