100% always pirate games from the major development corporations, don't give them your money, they're killing the industry.
Otherwise, I'll often pirate a game to try it out, and if I like it enough to see myself actually playing and returning to it, i'll buy it. I'm angry that game renting doesn't really seem to be a thing anymore, I miss being able to go to the blockbuster with my parents as a youth to rent a game for the week, why did we accept a new digital system that makes that impossible? The only other option is to download demos, and those are not the same in the slightest.