*There are some caveats with the use of all licences and public domain tools and it’s always worth checking that, in addition to copyright considerations, there are no other applicable rights in place which might restrict your use of the work (for example a visible brand or trademark). It is your responsibility to check for the existence of intellectual property restrictions, so don’t simply rely on the licence.
Key considerations:
check whether other rights exist in the work, e.g. trademarks
a Creative Commons work with a ND licence does not mean you cannot modify the work, but any adaptations you make must not be shared
a Creative Commons work with a SA licence requires you to similarly licence your adaptation. If you choose not to use a CC licence, here is a list of compatible licences
be careful not to violate licence terms, and to rectify them speedily if you do
Additional considerations when re-using work in the public domain:
it is still good practice to provide attribution to the creator of the work even though you are not obliged to do so (see attributing others' work)
works that are in the public domain in one country may not be in the public domain in another country, usually because of varying copyright terms. See the Wikipedia entry on copyright lengths.