In order to determine what information you need it's important consider the scope of your topic, i.e. where you need to focus your research and how broad or narrow it needs to be. This is especially important if you are required to choose your own research topic. If you are, it's also really important to check how much information is out there for you to draw upon; imagine spending ages choosing a topic to find that only a couple of books or articles have ever been written about it!
We've found two really useful 3-minute videos produced by North Carolina State University Library to help you better understand the importance of scoping: one called One Perfect Source? and another called Picking Your Topic IS Research!