It is essential to give proper attribution to sources quoted or otherwise used in your work. Using a source without giving credit to the author is plagiarism.
In addition to appropriate citation of resources that you use in your research, you should also be mindful of any copyright restrictions that might affect how you can use the materials in your work. The short videos available on the U.S. Copyright Office's website provide a good introduction. To get started, you can read this blog post "Six Copyright Concepts K-12 Students Should Know," or watch the following: "What Is Copyright" and "Fair Use" tutorial videos on the Copyright Learning Engine site.
Need help managing your research or long citation lists?
There are a number of free/open source citation management tools available to assist you in keeping track of citations, bibliography formatting, and more. These tools might also be referred to as reference managers, bibliographic management software, or citation managers. The majority share similar features: importing and exporting of citations; collect, organize and share; attach the article/file corresponding to the citation; and generate bibliographies in multiple formats and styles.
Looking for quick, on the fly citations? Most databases and electronic resource have built-in citation generators to help you format and create quick citations. In addition to the more powerful and in-depth citation managers at the top of the list below, there are also a number of free one-time use citation generators available in the second half of the the list that can quickly create a citation in a specific format.