The first thing is to make sure you clearly understand the assessment task and what topic you are seeking information for, this is called topic analysis. Checkout the Plan and Prepare for a (short) topic analysis video and the Common Instruction Words for helpful information. Check your Subject Outline for assessment details, and if unsure contact your subject coordinator for further assistance.
Now with an understanding of your task you then need to plan how you will search for information. This starts with identifying and brainstorming keywords, synonyms and related terms to use in your search for information.
Using synonyms can assist to broaden your search. A dictionary or topic specific encyclopedia may be helpful.
Macquarie Dictionary-online