Watch fantasy movies and check who you root for the most?
It also depends where you play. Some GMs handle certain classes very well while others badly so your favorite class might depend in what group you play.
I say it really depends on playstyle & whatever you like intelectually. I like magic, and I like to be in melee, but I'm not fond of "divine" classes, so I prefer Magus. (followed by wizard, followed by samurai)
However, most of my decisions are conceptual first. Table variations can make ANY playstyle fall apart, so I'd rather play something that I find interesting that something that might "match the playstyle I prefer".
