To keep in mind; to pay heed to or take note of something; to regard as important.
先生の忠告をよく気に留めておきなさい。
Keep the teacher's advice in mind.
顧客の意見を気に留めて、サービス改善に役立てる。
Take customers' opinions into account and use them to improve the service.
その点は上司に報告する際に特に気に留めてください。
Please pay particular attention to that point when reporting to your supervisor.