Databases will look different, but these tips will work for most databases.
Use these tips when searching for:
Write out your research question/topic and keep it handy. Refer back to your topic to check if a resource would be useful.
Track which search terms you have used in each database. This can help you not repeat searches, and you can realize if you skipped trying out a term.
Searching is iterative! You don't know if something exists until you try to find it. You'll likely need to try different combinations of terms.
AND limits your search results to only items that include both/all search terms.

OR widens your search results to include items with either term, regardless of how those terms relate.

NOT can eliminate the irrelevant phrases from your search results. NOT tells a database to not show any results containing that term. Be cautious. NOT can accidentally cut out relevant items from your search results.

Turn your research question into search terms.
Look at that article's keywords. Keywords are usually written underneath the article's listing in your search results.
Different databases use different keywords. By reusing the keywords, you are learning to speak that database's "language".
Some databases will give you suggestions for search terms when you start typing in a search box. These are terms that the database absolutely recognizes.
Sometimes, the suggestions will be several terms in the same text box, all separated by the Boolean Operator or. This means that the search engine will search for all those terms at once.
Always check before you select a string of terms. Some of the terms might not be equivalent for your specific research topic!