This can be approached from two angles:
If I watch a comprehensive gameplay video, it can appeal to my tastes. I know what I like and mostly can tell if I would like something by seeing it as a spectator.
In other cases, I would have to play with it a bit before I warm up to it. Years ago, I was stuck with one game that I borrowed called Space Colony. It looked mundane, but I had nothing better to do. After a while, I enjoyed it so much that I continued playing it while other games were available to me.
