When you first begin genealogical research, and even as you continue, it is important to take good notes. This means keeping a research log listing the sources you have searched and in which repository; what information was discovered; your reaction to that information, meaning does it pertain to your family or is it something to consider at a later time; and photocopies of relevant information listing the source.
Next, devise a way to organize these notes so you are able to locate them easily the next time you want to work on a particular person or line. Perhaps this is an Excel file or paper sheets stored in folders by person or family. And if your first system does not work, talk to other genealogists about theirs. Perhaps someone else has a way to tweak your system to make it work better for you.