Many databases and article collections, plus many e-books, will automatically create citations for whichever article or chapter you are viewing.
Look for a “Cite,” “CiteNow,” or “Cite This Item” button on the database record for the specific article or chapter.
(Not all databases have this feature. For example, LexisNexis does not.)
Examples of citation buttons:
EBSCOhost databases ProQuest databases JSTOR
(e.g., Academic Search Premier) (e.g, Newsstand)