You don’t wear anything to show you are a Sikh. You live by it to show it.
If a Sikh man or woman is Amritdhari (that has taken ‘Amrit,’ or holy water), they will be recognized by the 5 kakkars that every person blessed with Amrit must have on them. The 5 kakkars are kesh, kachera, kirpan, kanga, and kara.
Many Sikhs, man and woman, also do choose to tie turbans. Again, this has nothing to do with how much of a Sikh, or religious, that person is. However, the turban is very special to Sikhs.
Visit sikhism.SikhTruth.com to learn more.