
When Black has stones around on the outside and White approaches at 1, Black should play 2, securing the corner and not allowing White to settle easily. I've learned in the past from Guo Juan that when White attaches at 3, Black should make a good empty triangle with 4 and then cut at 6. Since Black has stones on the outside to help, the ensuing fight should be good for Black.

In one of my games in the London Open, my opponent played 3 here, instead of attaching. In the game, I played 4 at 7, but Black should still cut. The idea is the same: don't allow White to settle, and use your outside stones to gain the advantage in the fight. If White plays 7, Black simply extends to 8.

If White plays 7 here, Black makes a different empty triangle.

Even if White plays 3 as far away as N4, Black should still cut.

