For me, it's more remembering cues.

See a player targeted with big arrows pointing to them? Stack up.
See a circle with a pillar in it? Stand in the circle.
Different icons appear on the ground and the same icons appear over players heads? Stand on the icon that matches the icon over your head.
Targeted with a pulsing circular graphic? Run as far away from everyone as possible until the attack "drops" then run back to where the rest of the group is before the AoE goes off.

Other than that, it's mostly "Don't stand in orange on the ground.".

If you remember stuff like that, then remembering the more unique mechanics becomes easier(ie:2nd boss in Castrum Abania, who spawns three circles on the ground corresponding with ice/lightning/fire. Look at what buff the boss has and stand in the corresponding circle to get the appropriate buff, otherwise your damage is reflected back to you. So if he has a lightning icon on his buffs/debuffs bar you run into the lightning circle)