The guidelines followed by the Library of Congress, and therefore, by most other Anglo-American libraries are in "LC Rule Interpretation 1.0 Decisions Before Cataloging", which can be found at the Cooperative Cataloging Rules Wiki at:
Even before you begin to do anything, you must ask whether the specific item you are working with is a copy of something already in the catalog, or something new. That rather simple task is actually very complex.
They ask two apparently simple questions:
Before creating a bibliographic record, determine what is being cataloged. Answer these two questions:
1) What aspect of the bibliographic resource will the bibliographic record represent?
2) What is the type of issuance of that aspect?
Figuring out the answers takes you down some interesting paths. At the end of the Rule Interpretation, you will see some interesting guidelines that say what differences are allowed between one "manifestation" and another, e.g. different ISBNs do *not* have different manifestations.
I think it is important to realize that there is a great deal of variation between different agencies (publishers, libraries, other organizations) concerning what determines a manifestation and many libraries have their own interpretations as well. (For example, is a photocopy a new item or a new manifestation? Different libraries do different things) In any case, each field and each institution has different needs and I do not see agreement on any of this whether FRBR and/or RDA is accepted or not.
Message from the next day
I realize I forgot to mention "Differences Between, Changes Within: Guidelines on When to Create a New Record" from ALA (http://www.acrl.org/ala/mgrps/divs/alcts/resources/org/cat/differences.cfm), which also differs from the LC practice.
As a result from this multiplicity of guidelines which allow (or do not allow) for all kinds of variant, it is difficult to know precisely what information a specific resource has: what is the ISBN on the item, the number of pages, the precise dates on the item, and so on.