Way back in the day (pre 9–11) I learned a little trick, which I wouldn’t dare try today.
Back then large planes often flew half empty. I had no idea how they could afford to fly a half filled 747 from LA to Osaka routinely like that. Come to think of it, that airline is no longer in business.
Anyway, the trick was to wait in economy until after the in-flight meal had been cleaned up, lights turned down, and movie started. Everybody had to watch the same movie back then.
Soon after, most the cabin crew would disappear into the walls and at that point it was easy to walk up to business and take a few hour siesta in a much nicer seat. There might have been 5 other passengers in that whole section. No wonder that airline failed!
I stayed off the upper deck and out of the true first class section. I was brave, but not reckless.
When the lights came back on, I discreetly walked back to my rightful place in the back.
Actually I walked all the way to the very back which was even more empty than the front. That way I could see a better view of Osaka as we landed right in the middle of city without the wing blocking the view. (The airport has moved since then)
If I was on the left and something interesting came up on the right, I’d just switch sides. The whole row was empty!
I miss those days; I’m sure the airlines don’t.
UPDATE; Wow, thank you for all the upvotes! Your votes mean a lot to me, and to celebrate, I will share this memory of a more recent flight when I almost made it into first class. Happy travels!