This might also be a no-brainer, but to keep things organized I put entities close to the button/door/whatever that triggers them. For example: If a trigger_once fires a multi_manager, I place the multi_manager on one of the edges of the trigger_once brush. And let's say that multi_manager triggers a bunch of trigger_changetargets, then I place those entities in a neat row next to the multi_manager.
I remember, in my early mapping days I would place trigger entities anywhere in the center of a room or in a corner, and if the room contained a lot of triggers, this would result in quite a mess.