Dear (first name, if you are a relative or close friend, “Mrs., Mr., Ms.” and last name otherwise)
Body of letter
In the first paragraph, explain why you are writing, expressing your sorrow to learn of the passing and that you are extending your sympathy.
In the second paragraph, talk briefly about your relationship with the deceased and the positive characteristics they possessed that affected your life. Mention briefly something the deceased said or did that impacted your life.
In closing, express your hopes that the bereaved has good memories, and that their strength will carry them through this difficult time.
Warmest regards, Thinking of you
In writing your condolence letter, it is proper to indent paragraphs if you wish; it is also proper to write everything beginning at the left-hand side of the page, and simply skip a line between paragraphs to break them up.
A condolence letter will let the bereaved know you are thinking of them, and make them aware that their loved one did make a difference during their life time.