Fill the third cup of wine.

Thank God for the lovely, wonderful meal and the lovely, wonderful people you ate it with and the lovely, wonderful holiday you're celebrating. 

Say the blessing for wine again drink.

Fill the fourth cup in honor of Elijah the Prophet. Open the front door because Pesach is "leil shimurim" (lit. night of guarding) when God protects us against danger.

Ask God to protect good people and destroy evil, then close the door.

haggadah Section: Bareich
Source: Unknown