What's needed:
Unlimited amount of black and white stones.
A chequered board, measuring 19 by 19 squares. Beginners can use a 9 by 9 board.
Object
The basic object of the game is to surround the opponent's stones.
Rules
Players take turns in filling the corners of the blank spaces, called the intersection.
Black goes first. Placing a stone on the corner of the square. This leaves the opponent up to 4 chances to capture the opposing stone, (i.e. there are 4 lines out of a corner and once the white (for example) has been surrounded the white is captured and turns to black.
If there is a group of stones together, you'd have to surround the whole group with your colour.
The end of the game
Basically, it's all over when you've both had enough and have decided that you can't make more territory, capture more stones, or reduce his opponent's territory by playing on.