How can I tell if my lizard is dying?

if it is no longer moving or breathing, a sure fire way to check is to pick it up and try to open its mouth, if it resists, it's alive, but is probably very weak, also, some lizards, during the winter may go into bermation, which is basically hibernation but for lizards, if it's not winter, it's weak, you can help it by giving it reptivite, which you can get at most pet stores