Choosing the best license is important because Creative Commons licenses are irrevocable; the Creative Commons license applies to the work until the copyright on the work expires. Once you apply a CC license to your material, anyone may rely on that license for as long as the material is protected by copyright and similar rights, even if you later stop distributing it. This benefits others because they have confidence knowing you can’t arbitrarily pull back the rights granted them under the CC license.
Creative Commons licenses apply to the work itself and all copies of the work made after a license is applied.
Each of the Creative Commons licenses requires acknowledging the author and attributing the work. CC licenses allow for flexibility in the way credit is provided depending on the medium, means, and context in which a licensee is redistributing licensed material. For example, providing attribution to the creator when using licensed material in a blog post may be different than doing so in a video remix. This flexibility facilitates compliance by licensees and reduces uncertainty about different types of reuse. U.S. Copyright law does not usually care much about attribution or correct citation, but with a Creative Commons License, you receive attribution as a condition of all of the licenses.
When attributing others, a good rule of thumb is to use the acronym TASL,
Pay attention to any copyright notices, such as a notice that refers to the disclaimer of warranties or a notice of previous modifications. Best practice is to just retain everything by copying and pasting such notices into your attribution. Don't forget to note in the attribution if you modified a work.
If you have any doubts or questions, you can read the complete attribution requirements, which are spelled out in detail in the legal code of every CC license. This chart compares the detailed requirements across all versions of CC licenses. Note that the CC0 tool allows use without credit.