Every publication type has some specific metadata that should be given in any citation.
For a book, these would be:
- Authors or editors for an edited book
- Year of publication
- Information on the publisher (mostly name and address)
For a journal article, you should include:
- Title of the article
- Title of the journal
- Volume of the journal
- Page numbers or article identification number for journals without page numbers.
Generally, looking at the required fields for a bibtex entry may give you an idea of what are the required pieces of information for any publication type.
Note that some journals don't generally include the title for journal citations, but I find that inconvenient for the reader. There may by additional information depending on the citation style, for example the issue number for citing journal articles, URLs, ISBN/ISSN. But these additional pieces of information, the formatting and even the ordering of the information in the reference generally depend on publication venue, as Suresh wrote in his answer. The key information however should be the same for each citations style.