Even if your intentions are good, you may commit plagiarism without meaning to do so, for example, paraphrasing a source instead of using a direct quotation. Even if you rewrite the words or ideas coming from others, you are still required to give credit to the original source, and failure to do so is plagiarism. Another potential problem occurs when you don't put your citation in the right place. Introduce your sources explicitly and include citations at the end of the relevant information to make it clear which ideas are from your sources.
The ability to research a topic and use it to validate your ideas and viewpoint is critical both academically and in careers based on the written word. Writers who plagiarize find it easier to copy or adjust the words of others for their own use because they have not developed proper interpretation and analysis skills. Becoming a skillful researcher will steer you away from the danger of plagiarizing.
In the course of your research, you will come across information from a variety of sources you plan on using later. Make it easier on yourself by saving a copy of each source for future reference. Print out Internet documents, make photo copies of individual pages in books containing borrowed information or compile a list of all the locations your sources came from. As you include the information in your writing, be sure to give credit to the appropriate source.
Attributing information to a source is not always a black and white decision. The rule is to use a citation any time you state an idea that is not yours, with the caveat that information that is common knowledge does not have to be cited, such as writing that at there are 50 states in the United States. Some cases are not quite so clear-cut, however. If you have any doubt about the necessity of citing your source, don't take any chances -- cite it. You may also get the opinion of your instructor before turning the paper in.