I used a book to prepare for a presentation I gave in class. I just paraphrased some of the author's ideas - I didn't quote directly from the text. Do I still need to include it in my references?
Whether you are presenting the information in a paper or an in-class presentation, whenever you quote or base your ideas upon someone else's work, you must credit your sources, providing the fullest bibliographic information possible. This applies to resources you use such as class notes or web content such as blogs or wikis. Citing your sources is important so that others can further explore the topic if they wish to. Even more importantly, it is crucial to give credit to the author of the original work. If you directly quote or even paraphrase from a work (unless the idea is considered common knowledge) without providing a source, that constitutes plagiarism.
With both published print works and information found on the Web, there are guides to help you cite properly whether you are using APA, MLA, Chicago, etc. citation styles.