Can you tell a chick's gender by how many layers of wing feathers it has? Someone said they could when I bought some chicks. I personally don't believe him. I do NOT want a rooster!
Sometimes you can sex them by the layers of feathers when they are less than four days old. It is not always accurate though...
You could always forego the chick stage and buy an older hen. Thus a guarantee you do not have a rooster.
Or you can buy sex-linked chicks. Hatcheries also often have the option of getting just pullets in your order, so that's a good way to go if you don't want roosters.
