look at what the firm's 'key competencies are', and if not, consider generally for trainees.
Find ANY achievement, team success, something where you get a job done and there's been obstacles. Examples can depend on what stage you're at (studying or in work). When I was studying I talked about part-time work achievements/promotion; when I was a uni sports captain and boosted membership and won the league. When I was a Paralegal I talked about deals I'd worked on, what I spotted, getting transaction done in the timescale so they could make the most commercial benefit from the acquisition etc.
Talk about what you did, not what the rest of the team did, skills/competencies employed, how you overcame challenges.
what was the result and what was achieved
Go through the STAR technique when preparing