A systematic search starts with a clear and focused research question. Once you have a good research question:
If you use more than one search term in your search, most search engines will look for documents in which all entered terms occur. Would you like to combine search terms in another way? In that case, you need to use so-called operators. This search method is also called a Boolean search (after George Boole).
The operators most frequently used:
You can combine operators, much like in mathematical equations. ‘AND’ takes priority unless you use brackets to group concepts: (youth OR adolescent* OR "young adults") AND (bully* OR "peer harassment").
Please take note: operators and wildcards may differ among search engines.
Other techniques you can use:
By dividing your research question into elements, you get a better overview of your search results and the parts of your search that might need improvement. For each element, try to find keywords that relate to that topic, words or phrases that you would expect to find in the title or abstract of relevant papers.
In most databases (not Google Scholar) you are able to perform searches for each element and then combine those searches in the Search History.
By combining those elements with AND, you will only get articles that match all elements and are therefore potentially relevant to your research question.