Have access to the Adobe Creative Suite, including Photoshop, Illustrator, and CorelDraw.
Be proficient with using a computer, although prior knowledge of any of the Adobe apps is not necessary.
Some creative skills (drawing, photography, etc.) are helpful and will definitely give you a better chance at becoming successful as a designer, but not required.
A desire to learn design, whether for a job or for a hobby - design is for everyone!