If you would be a light to the world, as the Savior enjoined His Saints to be, then you should strive to leave positive things in your wake, wherever you go.

For instance, suppose you go to the doctor's office.  There are five things that you can leave behind.

First, you should leave a good impression.  The receptionist, the nurse, and the doctor should all remember you as a happy, positive person.

Second, you can leave a compliment.  That will put a glow in the recipient's mind which might last all day.

Third, be sure to smile, even when you catch the glance of another patient in the waiting room.  There is a reason that he or she is called "patient."  The person is there because of a worry, and your smile will be a perfume that will leave the atmosphere brightened even after you leave.

Fourth, you should leave your own worries and problems elsewhere, and not carry them around.  You do that by not being a complainer.  Lehi told his son that the Lord "shall consecrate thine afflictions for thy gain," (and I add), "if we resist the urge to complain."  (2 Nephi 2:2).  No one likes listening to a whiner.

I prayed for a thought to come to me from the Holy Ghost that I could write about.  I closed my eyes to think.  I was dozing off when I saw a doctor's office, and had the random thought, "Leave five things behind."  I opened my eyes, and began to write, not knowing what the five things were.

I've identified four of them, and am looking for the fifth.  It must be a testimony.  If the opportunity is there, and presents itself, seize it, and leave behind a portion of your testimony.

A good impression, a compliment, a smile, your own problems, and your testimony.  Those are the things you should leave behind, and you will be a light to the world.