If you do a friend a favor, your friend will probably be appreciative, meaning grateful. Use appreciative to describe words and actions that are positive, either out of gratitude or respect.
If you know that appreciation is a type of respect and admiration, then you won't be surprised by the meanings of appreciative. Children should be appreciative of everything their parents do to take care of them. We can also say a positive review is appreciative, showing that the critic likes and appreciates the subject of the review. Appreciative words and gestures are always positive and respectful.