step 1: go to your local motorcycle gear store that carries at least a couple major brands. most will carry astars and maybe even sidi. try on a couple different boots, and you should write down the numbers (along with model of the boots) that fit best. if you try on a sidi mid level boot, the racing boots will probably fit the same. hell, i just took the sizing info from my puma sneakers and ordered my puma racing boots and they fit perfectly. obviously, trying on the ones you are going to buy is the best method, but there is nothing wrong with well educated guesses. this applies for all gear purchases. once you have that sizing info, get online, search ridemerchant, weraclassifieds, 2ontrack, and search google for: site:craigslist.org boots (or gloves, condoms, lube, etc) buy them used to save a bunch of money, but make sure you see good pics first. good luck out there!