In general, choose sources which are most recent, most authoritative, and most complete in their coverage.
The Langara Library has a wide range of materials and offer in-depth research help. Start with the Library Website.
Once you have selected your topic, the next step is to find research material. For certain topics, you will want to find primary as well as secondary information sources. Primary research is a direct first-hand study of the topic; its sources are observation, questionnaires, interviews, inquiry letters, works of literature, or personal documents (letters, diaries, journals). For instance, if your topic is welfare in Vancouver, primary sources would include interviews with welfare families and government personnel. Secondary research is based on information and conclusions that other researchers - - by their research of primary information - - have compiled in books and articles. Whenever the topic permits, try to combine these two types of research.
Consult a wide variety of books, scholarly essays, magazine and newspaper articles, reports, etc. Don't base all or most of your information on a single source. Also, don't just read literature and interview people who support your own viewpoint. Look at material that supports different and opposite opinions to give you a more comprehensive view of all the issues involved. Readers are more sympathetic to a writer who can see all sides of an argument objectively, and who is more interested in seeking the truth than in bludgeoning readers with his own knee-jerk opinion. If, after all your research, you still feel strongly committed toward a certain viewpoint, you should still give a fairly full and just presentation of the opposing viewpoint. You may even concede that some of the other side's ideas are valid or party valid. The stronger you present the opposing point-of-view, the stronger your own viewpoint will emerge in having to battle against it. With only a weak opposition to confront, your paper itself may be weak.
Remember too, as you are writing your essay, that there are few issues in the fields of sociology, politics, medicine, etc. that are simple. Take account of the multiple and subtle issues involved. Don't gloss over the complexity of something.