Reference managers (or reference formatting software such as BibTeX for LaTeX documents) make it easy to organize and format citations. They can also assist with managing libraries containing citations, PDFs, and image files by organizing important documents by subject and allowing you to search your library using keywords. Add and organize any papers that are relevant to your research as you read them. This will help you remember to appropriately cite articles that you have read.
TIP: When using a reference manager, make sure you have the correct style file for your target journal. The reference style used by the journal can usually be found in the Instructions for Authors on their website. Formatting references using a reference manager with a style file is very simple.