Aren't the purposes of concentration camps in the name? To concentrate a troublesome population in a manageable area. Most deaths were due to bad management or disease. That's why I prefer to use the term extermination camps when referring to the Nazis.
Well, while some of the camps (Auschwitz and the like) were extermination camps, not all the German camps existed for the purpose of killing their internees (which was, for the Nazis, a happy result of their mistreatment and conditions of the internment), the great majority of the camps existed for concentration purposes, or for provision of forced labour.
Regarding the actual question, I agree with Dirty Commie, the best way would have been for the Boers to not try and besiege the South African towns, but instead to fight a more coordinated guerilla campaign to frustrate the British. Home opinion expected the war to be over within months, as the war dragged on without any sign of an end and casualties mounted up due to fighting and disease, the support of the press and parliament would inexorably wane, perhaps forcing an end to the war.