From U of I at Urbana-Champaign:
The STAR method is a structured manner of responding to a behavioral-based interview question by discussing the specific situation, task, action, and result of the situation you are describing.
Situation: Set the stage for the interviewer by providing an overview of the situation and any relevant background information. Be specific and succinct.
Task: What goal were you working toward?
Action: Describe the actions you took to address the situation with an appropriate amount of detail. What specific steps did you take and what was your particular contribution? Use the word “I,” not “we” when describing actions.
Result: Describe the outcome of your actions and don’t be shy about taking credit for your behavior. Your answer should contain multiple positive results.
Make sure that you follow all parts of the STAR method. Be as specific as possible at all times, without rambling or including too much information. Often times the interviewee must be prompted to include their results, so try to include that without being asked. Also, eliminate any examples that do not paint you in a positive light. However, keep in mind that some examples that have a negative result (such as “decided to go around”) can highlight your strengths in the face of adversity.