What size Toms Shoes should I get?

I am getting the classic style. My shoe size just depends on the shoe, so I really don't know what size to get. I can wear an 8 in some, an 8 1/2 in some, and a 9 in others. I have had these before a href="http://www.payless.com/store/product/detail.jsp?catId=&subCatId=&skuId=087108055&productId=69780&lotId=087108&category=&catdisplayName=Womens" rel="nofollow"http://www.payless.com/store/product/det…/a and I know that they are similar to Toms, and I wore an 8 1/2 in those, so if anyone could give me advice it would be appreciated. Thanks!