In science, it is preferable to express the idea(s) of other authors in your own words, rather than directly quoting an author's work. However, even though you are expressing the ideas in your own words, it is important to give credit to the author both within the text of your work and at the end of your report or presentation in a bibliography. The act of referencing your sources(s) in your work and in a bibliography is called citation.
TIP: If you get into the habit of taking notes in your own words and recording the source of the information as you read as recommended in strategy 2, then you won't run into any difficulties when you are writing up your assignment.
Citing references requires having the correct and complete information about the item. This means that you always record the author(s), year of publication, title, journal, volume and pages for a JOURNAL ARTICLE, and the title, author/editor, publisher, place and year of publication for a BOOK. If you use a chapter in an edited book (i.e. the chapter is written by one person, and the book is edited by another person), you will also need to copy down the title, author(s) and pages of the chapter in addition to the title and editor(s) of the book.
TIP: Write down the full citation when you first look at a source or copy some pages. This will save you a lot of time when you are preparing the bibliography for your assignment.