Think about what you actually want to search for.  Write down your assignment topic, your assignment answer idea, your study topic  or the idea behind whatever you want to search for. To help with the phrasing, you could, for example, look at a textbook or an encyclopaedia to get an idea of the kind of words you could use in your search

Remove the words that are not going to be useful for your search; search engines of any type search for exactly what you enter as a search terms, so try to remove anything that isn't needed

Identify any limiters or restrictions, for example geographical locations, historical periods, population groups.  These can help you refine your search

Think about other terms that might describe your topic. Look at a dictionary or thesaurus for alternate ways of expressing a word or phrase.

Some questions to ask:

Here's a template that you can download to help with planning and building your search