The amount of information currently available, the different media and presentation formats joined with the little time availability of the researchers and people in general, make necessary the implementation of automated tools selecting and evaluating information, aiming at not only optimizing resources but also obtaining useful and personalized results that optimize the daily work of its users. A technique known as information filtering could be seen as a solution to this problem. Within an information filtering system, a user introduces a profile in the system which represents his/her information needs; then, the system works to display the relevant information. We contain a sample of the research carried out in this important area, focusing the work towards two most representative techniques: "content based filtering" and "collaborative filtering". These techniques have been studied from different points of view, allowing to create a solid framework which involves the necessary criteria for designing and creating a tool using the most outstanding characteristics of each technique. They provide a view to facilitate the work of people devoted to the search, depuration and distribution of information.