The following techniques can improve your searches in many article databases*
Enter phrases in quotes: "global warming" "capital punishment" "organic food"
Use truncation symbols to search for alternate word endings: In most databases, entering ethic* searches for ethic, ethics, ethical and ethically
If one term doesn't work, try a few others. Experiment with different vocabulary related to your topic. Brainstorm ideas for relevant keywords and use background sources such as Wkipedia or CQ Researcher for suggestions.
*Note: individual databases might have varying conventions for how to search. Consult Help or Search Tips within databases or ask a librarian for help with searching