References are necessary for all papers that include a research component. The basic idea: if you are using thoughts or words that did not come from you, then there's some citing to be done! Having accurate references in your paper is a big step towards gaining credibility with your reader.
Plagiarism. The major concern of pulling ideas from other sources to include in your own work is a kind of academic dishonesty that's called "plagiarism." This is important because ideas are considered the property of the author, and by using others' ideas without giving them credit, you are claiming those ideas as your own. This kind of intellectual theft, whether it was intentional or not, comes with academic consequences.
Academic Sources. As students are constantly reminded, "ANYONE can put ANYTHING on the internet." In academic writing, it is important to avoid using sources that may not be accurate or reliable. This means that a quick Google search will probably not offer the most helpful sites. However, decent and reliable places to find information (such as your library databases) do exist! See the box labeled "More About Academic Sources" for further information.
Formatting is another essential part of successfully writing an academic paper. A paper with correct formatting helps to keep your work more organized and your reader's attention more focused.
For questions on punctuation and grammar specifically, see the Basic Grammar And Punctuation Guide