Before you start searching, it is useful to get a sense of how scholars talk about your topic and relevant adjacent fields. Reference resources can be a great way to do this. 

Many databases or discovery tools (like Catalyst) will prompt users to start with a very broad keyword search. This kind of search will maximize your number of results, but sometimes this can be overwhelming. By looking for the option to do an advanced search, you can build nuanced searches that return more focused results.

TIPS:

If you're looking for a specific, known item, consider searching with the "title" or "author" field selected.

If you're looking for sources about a topic, consider searching with the "subject" field selected.

Most resources anticipate that users will enter their search terms the same way that they talk about them. This is called a "natural language" search. You can also use Boolean operators to perform searches. Often the most useful Boolean operators are AND and OR.

AND can limit results by requiring that multiple terms are included in order to appear in a result set.  

OR can expand results by allowing for any of a set to be included. This can be particularly useful when you want to search using multiple terms or synonyms for something. 

You can augment these Boolean operators with quotation marks, parentheses, and asterisk, in order to build out your search more fully.

Quotation marks search for an exact phrase within the marks. Parentheses create a sub-search within your search string. An asterisk allows for variations of a word. 

Here is an example combining all of these techniques: (HIV OR AIDS OR "Acquired Immunodeficiency Syndrome") AND art AND politic*

Any items that have either the words "HIV," "AIDS" or exactly the term "Acquired Immunodeficiency Syndrome"), limited to items that have the word "art" as well as a variation of words that start with "politic," such as "politics," "political," "politician," etc.