I would first of all make myself out to be weak during the training to make the other tributes believe that I am not a threat. I would make no alliances either. Once in the arena, I would grab the pack/supply furthest from the cornucopia and run into the forest. Once in the forest (assuming that it is a forest type arena) I would scope things out while others are still fighting in the cornucopia. Then I would find a place to hide. Assuming I managed to grab/make a bow and arrow, I would kill other tributes like how a sniper would, choosing to remain unseen. Of course, there would be certain tributes that I would rather not kill, for any reason, and leave them to each other. I would hunt, and if I had to cook meat, I would start the fire in a spot away from wherever my camp was and use the driest wood, for hope of less smoke. .. after that I'd just hope for the best!