個 (こ)
Small & compact objects; round fruit, balls, and boxes.
冊 (さつ)
Bound objects; books, notebooks, and magazines.
本 (ほん)
For long cylindrical objects; trees, sticks, pens, bananas, and fingers.
枚 (まい)
For flat, thin objects; paper, dishes, stamps, blankets, and boards.
匹 (ひき)
For insects, fish, and small animals (cats, dogs)
頭 (とう)
For large animals; horses, bears, and deer.
羽 (わ)
For birds.