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.
CC licenses have a flexible attribution requirement, so there is not necessarily one correct way to provide attribution. The proper method for giving credit will depend on the medium and means you are using, and may be implemented in any reasonable manner. Additionally, you may satisfy the attribution requirement by providing a link to a place where the attribution information may be found.
While the attribution requirements in the license are the minimum requirement, we always recommend that you follow the best practices for the kind of use you are making. For example, if you are using scientific data marked with CC0, you are not required to give attribution at all, but we recommend that you give the same credit you would give to any other source—not because the license requires it, but because that is the standard for letting others know the source of the data.
The CC website offers some best practices to help you attribute properly, and the CC Australia team has developed a helpful guide to attributing CC-licensed material (.pdf) in different formats. Note that the attribution and marking requirements vary slightly among license versions. See here for a chart comparing the specific requirements.