Plagiarism is a serious offense, and in the real-world it comes with serious consequences. You should ALWAYS cite your sources- whether it is a quote, paraphrase, or indirect quote.
The resources below will assist you with citing your sources properly. BUT they are not a replacement for your brain! Make sure to check your citations and ensure that they are written correctly and include all of the necessary information for your teacher. Your citation is a coordinate, and should lead your teacher easily and quickly to the source that you used.