All CC licenses require users to attribute the creator of licensed material, unless the creator has waived that requirement, not supplied a name, or asked that her name be removed. Additionally, you must retain a copyright notice, a link to the license (or to the deed), a license notice, a notice about the disclaimer of warranties, and a URI if reasonable. For versions prior to 4.0, you must also provide the title of the work. (Though it is not a requirement in 4.0, it is still recommended if one is supplied.)
You must also indicate if you have modified the work—for example, if you have taken an excerpt, or cropped a photo. (For versions prior to 4.0, this is only required if you have created an adaptation by contributing your own creative material, but it is recommended even when not required.) It is not necessary to note trivial alterations, such as correcting a typo or changing a font size. Finally, you must retain an indication of previous modifications to the work.