A man's physique is different than a woman's, so it may be difficult to find women's clothing to fit. Taking accurate measurements and consulting clothing size charts can be helpful. However, clothing size varies with each clothing manufacturer. Until you're comfortable trying on women's clothing in a store, here are some tips to help you determine your size.
Measure from shoulder to shoulder. Since a man's shoulders are usually wider than a woman's, you may have to buy a larger size blouse and have the waist taken in by a tailor.
Check your waist measurement at naval level, not at the belt-line. Many women's pants are made to fit a smaller waist and rounder hips. You may need to buy a larger size and have them tailored to fit around your waist and hips in order to have them hang properly.
Consider your height and weight, and look at a clothing size chart. Most Internet clothing shops have charts to give you a good idea of a range of sizes you may be able to wear.
Visit a used clothing store or a thrift shop to purchase several pieces in the size range you've determined will fit, and take them home to try them on. This will give you a sense of what fits without spending a lot of money.
Check out online clothing stores that specialize in transgendered clothing, such as Janet's Closet.