Read a book about feelings to the children. "Today I Feel Silly: And Other Moods That Make My Day" by Jamie Lee Curtis or "How Are You Peeling?" by Saxton Freymann and Joost Elffers are two good choices.
On chart paper, list four common feelings that children will know: happy, sad, mad, scared. Discuss each feeling and have students give examples of when they felt that way.
Discuss how people look when they feel certain ways. Call out a feeling and have the students make a face to go with it. They smile when you say happy or frown when when you call out mad. You might let individual students demonstrate their different faces.
Show the students pictures of people in different situations, feeling different ways and discuss them with the class. Talk about how the people in the pictures are feeling and why. Also talk about what you should do if you see someone in that situation.
Give each student a sheet of paper and crayons. Tell them to choose one of the four feelings you have talked about and draw a picture of a time they felt that way. On another day they can share their pictures with the class.