Mark your research notes with clear indicators of what ideas are yours and what ideas came from others. You're effectively writing formal research notes when you write a literature review, so your informal notes must be more meticulous than usual. You might falsely remember an idea from your notes as yours later, so it is important to include references even at the earliest stage of research.
Keep a list of every source consulted in your research, whether or not you use that source in your final review. It is better to cut sources out in editing than to completely forget to acknowledge them.
Use quotation marks or indentation to mark any direct quotes used in your review annotations. Because annotations build upon an existing work, you need to make a clear definition of what words are yours and what words belongs to others or you risk confusing your reader.
Indicate the source of paraphrased material with in-text reference to the original source or a visible footnote. Since paraphrases don't have visual indicators such as quotation marks, you need to use language and footnotes to make it clear that the idea is not yours.
Give credit to the sources of any statistics or technical information you use to enhance your analysis of included texts. Even if a fact seems obvious and thus common knowledge, if it comes from a formal study you should cite that study.