"Wine goblets are placed at each setting for each participant, and a decanter of wine is prepared. The wine goblets are to be filled four times in the course of the Seder. At normal Sabbath and festival meals a cup of wine is served for kiddush and another when the aftermeal Grace is recited.
But because of the joyous nature of Passover, two additional cups were added. One is consumed after the `story' of the Haggadah is read (which ends before Grace), and the other at the conclusion of the service (just before the hymns and songs)."
(The Family Seder. Prepared by Rabbi Alfred J. Kolatch. Jonathan David Publishers, Inc. Middle Village, New York. 1991 by Alfred J. Kolatch)