It is important to understand what the instructor is asking in order to successfully complete the task. Before running around the library, surfing the web or camping out at a computer to do research, take a few minutes to think about what is being asked of you. Realize that this takes much longer than you would expect. Think about what needs to be done and plan accordingly.
Different disciplines require various types of materials.
On the other hand, the humanities use a variety of older and current information so a 100 year old book might be better for your research than yesterday's article. If the assignment is still unclear, check with your instructor.