How does Odysseus ensure that his best men aren't killed first?
Odysseus cannot - and does not - ensure that his best men aren't killed first. In the cave of Polyphemus, for instance, it is only by chance that when the lots are drawn the four ablest men are selected to blind the cyclops. And in Book 12, it is his own first officer - Eurylochus - who leads the mutiny and kills the cattle of Helios. Each man's life is in the hands of the spinners - and the consequence of his own poor judgement, and try as he might, Odysseus cannot protect them, nor make certain that only the weak are killed off first.