The man who is the head of the family, standing at the entry door, throws roasted soybeans (called fuku mame - fortune beans) outside or into someone wearing an oni (demon) mask, while the rest of the family shouts:
Oni wa soto! Fuku wa uchi! (Out with the evil! In with good fortune!).
Then the door is slammed hard to prevent the oni to enter. So, the oni is chased away by the soybeans and the good luck enters the house.
Mamemaki also takes place at shrines and temples. Priests and guests (usually sumo fighters or stars) are throwing roasted soybeans (sometimes wrapped in gold or silver foils) into the mass of people. Then, it is said that if you want to be healthy all year long, you need to eat a number of bean equal to your age... That's quite easy, because I tasted these beans and they're not bad...
Years ago, I was intrigued by an interesting mosaic at the entrance of the Asakusa Tokyo Metro Station (Ginza line): it represents several events taking place at the Senso-ji Temple throughout the year.
So, I started to decipher it... and here's the detail regarding Mamemaki: in the center, colored in red, with horns and fangs, is an oni head - he looks quite upset... And to the left, in front of the temple, three traditionally dressed men are throwing soybeans...
EXIF info:
Nikon D90
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 20mm
Aperture: F/5
Shutter Speed: 1/40s
ISO Sensitivity: ISO 200