How To Get Free Upgrade to 1st Cl on International Airfares?

In real life, it is very difficult to get a free upgrade to 1st cl. The plane would have to be overbooked and, even then, travelers are usually just offered an economy ticket for another date or perhaps a free economy seat. It used to be much more common to get an upgrade than it is now. First cl sections are often full and I have found that it is not that easy to pay for an upgrade once you've booked an economy ticket. I would say your chances are slim to none. Sorry.