You don't go about it at all. It's totally random and just one of those things.
If you wanted a strategy though, travel at a special occasion like a birthday or anniversary and mention it on your reservation and when you check in, you never know what could happen.
You should never expect an upgrade though, and never be disappointed if it doesn't happen for you.
Best bet is to book the resort and room category you will be happy with and hope for the best.