When you look at a citation you should be able to tell what kind of source it represents.
Books will always have a year of publication instead of a specific month, day, or season and will also include a place of publication.
Magazines, journals and newspapers all have more specific dates and will have an article and a publication title.
Journal articles tend to have more scholarly titles, both of the articles themselves and of the publication, often including the word "journal" in name of the publication. In MLA style, volume and issue are included with journals, but not with magazines or newspapers.
Magazines and newspapers tend to have more catchy titles. Newspapers are usually published daily and often include the name of the city in the newspaper title. Magazines are usually published weekly or monthly.
Web pages may also be magazine, newspaper, or journal articles or even books, or sometimes they are original content not included as part of one of the other types. In APA style the URL for the web site is included. In MLA style, web is always mentioned as the medium.