One of my PCs has been using a trident and net, which I was treating like a spear, but now I'm not so sure this was the best interpretation. It seems that tridents would be harder to throw than a spear. That makes me think they might ought to be classified as a pole arm, but when I've seen tridents pictured they're usually wielded in one hand. Should I treat the trident as a standard 1d6/1d8 weapon that just looks similar to a spear?
The Players Companion mentions tridents under the Templates for the Thrassian Gladiator (Beastfighter & Gladiator Trainer), where it is treated as a type of polearm.
Given that polearms require two hands to use, and tridents were evidently useable one-handed, I would treat them as spears. If you want to get high-detail, reduce their thrown range and give them some other bonus. Bonus to disarm by catching weapons with the tines, perhaps?
You could treat it as either a spear or a pole arm, depending on the size of the trident and how it's deployed.