Giving credit to the original author by citing sources is the only way to use other people's work without plagiarizing. But there are a number of other reasons to cite sources:
Not at all. Citing sources actually helps your reader distinguish your ideas from those of your sources. This will emphasize the originality of your own work. It also gives you greater credibility because you are demonstrating your knowledge on the subject and your understanding of the work that's already been done by others on the subject.
Whenever you borrow words or ideas from another source, you need to acknowledge that source. The following situations almost always require a citation:
The Limestone University OWL (online writing lab) is the virtual extension of the Writing Center on the main campus. The LU OWL offers live peer tutorial sessions to all students. On campus students may visit the Writing Lab in person.