The art of spoiling winning positions without blundering is something I used to be very good at. When you've outplayed your opponent and reached a winning position, notching up the full point should be a matter of technique, but I can recommend some reliable paths to lose your way.

One of the simplest is to insist on analysing only forcing variations. It is easy to overlook an effective quiet move at the end of a long, forced sequence. Once you have slipped into the groove of looking at moves containing heavy threats, it can be difficult to move back into more positional mode.

Taking this a stage further, it is surprisingly easy not to play a very strong move - but one with no direct threat - simply because you can't find a decent reply for your opponent. If you can't find a move for him, you can't analyse it, so you move on to something else.

Jon Speelman is too strong and imaginative a player to fall into such lazy thinking habits, but the finish of his game as Black against Eric Lobron in Berlin this year gives a good illustration of the temptations. It was Black to play in the diagram position. With two pieces for a rook, and an exposed white king, Black is clearly winning, but how to finish it off?

The natural thing to look at is 1...Rb1+ 2.Kg2 Qb2+ 3.Kh3 (3.Kf3 g4+ 4.Ke3 Qd4+ leads to a quick mate) 3...g4+ 4.Kh4, but now what? After 4...Rxh1 5.Rxh1 Qg2, White defends with 6.Qe1. Black cannot get his queen on to the c1-h6 diagonal to mate on h6.

There is no good forcing move after 4.Kh4, but Speelman found the devastating 4...h6! Now 5.Rxb2 Rxh1+ is mate next move, while 5.Qd8 Rxh1 6.Rxh1 Qg2 leaves White defenceless. Meanwhile, Black even threatens 5...Qg2! In the face of all this, White resigned.