Our national organization, the American Go Association, has a good webpage on their website, that summarizes your online options for learning Go.
The game is for two opponents, or two teams.
Black plays first. Then White plays a stone, then black plays a stone, and so on.
Stones are placed on the intersections, not the squares.
Once a stone is placed on the board, it is not moved for the rest of the game unless it is captured.
When a stone touches another stone of the same color along a line, it loses its individual identity and becomes part of a group. Groups can have any number of stones, limited by the size of the board.
A stone or a group of stones must touch at least one empty intersection along a line to remain on the board. These empty intersections are called “liberties”. When all of the liberties are filled by the opponent, the stone or entire group of stones is captured and removed from the board.
The other rule, called ko in Japanese, prevents repetition of a board position.
Play ends when both players agree that any more moves they make in the opponent’s territory will be captured, so they choose to pass instead of playing more stones. One of the ways to score is to count the empty intersections that a player controls. Another scoring method is to fill in any empty intersections with stones of the surrounding color and then count all the stones on the board. Whoever has the larger number wins.
If you are a beginner, the hardest part of the game will be knowing when you are finished, and it is time to say “pass”. It is very helpful to have an experienced player available to show you the finishing moves.
A simplified method of play is to end the game as soon as either player captures any stones. This method is easier for beginners to learn, especially on a small 9×9 board. A more advanced method is to end the game when five or more stones are captured. This makes the play more complex because it makes it possible to sacrifice one stone to gain more captives from your opponent, but this version is still easier than the full game of Go described above.