The moment a work is created and fixed on a tangible medium it is automatically protected by copyright. There are no formal procedures necessary. This means, therefore that anything fitting the above criteria is protected, not just published material, thus also emails, letters and assignments are copyright protected.
Although not legally required, a copyright notice along with your contact details, is a recommended sensible addition to your published work. The way third parties can contact you if they wish to reproduce or re-use your work. An example of a good copyright notice is: ©A. Nonymous. For permission and questions contact A.Nonymous@email.com