Using quotes... copyright laws?
It depends where you are in the World, when the piece to be quoted was written and in what context you want to use the quote.
In the UK we have the UK Copyright Designs and Patents allows "fair dealing" with a copyright work for the purpose of criticism or review, provided that it is accompanied by a sufficient acknowledgement.Any creative work is automatically copyrighted in the UK but I think not in some other countries.
If the work is out of copyright you can use any or all of it, but if in copyright and not to be used in a critisism, educational or news context then you would need to contact the publisher or author.
This could explain why Shakesperean & Biblical quotes are used for so many plays, films & books!
This might help for UK http://www.copyrightservice.co.uk/copyright/uk_law_summary
The Berne Convention will be more use if you are in USA
And just did a quick google for USA laws http://www.copyright.gov
 See also