The chances of an asteroid from the asteroid belt hitting Earth are very close to zero. The chances of a so-called "near Earth asteroid" hitting Earth are much higher... in fact, they hit Earth all the time, and are seen as meteors ("shooting stars").
Apophis is an 885 foot diameter asteroid that will pass by Earth on April 13, 2036. The odds of it hitting the Earth are calculated to be 1 in 48,000. Keep in mind that the asteroid that crashed into Chicxulub, Mexico wiping out the dinosaurs was 6 miles wide, nearly 36 times larger.
Asteroids hit the earth every day. The small ones burn up in the atmosphere and fall to earth as dust, occasionally larger ones my hit the earth surface. Most of these will land in the ocean. The odds of a person being hit by a meteorite is minuscule.
Usually by another asteroid moving through the belt and hitting one, creating a force to move an asteroid from its orbit. Also, if a large enough asteroid passes by, it is possible that the gravity that it generates could pull a few off.