Take some maror. Dip it in charoset, then shake off the charoset. Recite the following blessing:

Baruch ata Adonai Eloheinu melech ha'olam asher kidshanu b'mitzvotav v'tzivanu al achilat maror.

Which means:

We bless you, Lord our God, God of the world, who has sanctified us with his commandments and commanded us concernint the eating of bitter herbs.

Eat the maror immediately. Do not lean while you eat the maror. 

haggadah Section: Maror
Source: Unknown