Some cargo operators, flying long haul and crossing many zone time, give you courses about sleeping management but it's always a personal matter, some people are able to sleep easier than others. Basic rule is eating good food, not too much, no alcohol and try to take a nap before your flight. Avoid chemicals that help you sleep because many of these medicines are used to regulate the sleep at the same times and usually cargo or long haul flights are never the same times when you should sleep.
