What Unholy said is a waste of locations, just have separate triggers depending on which hero they pick and center the location, so it only requires 12 locations total, rather than wasting 84 locations.
U require the trigger per hero in order to shorten other triggers.. Such as spell effects. If u haven't played Temple Siege before, there's a paralyzing trigger where the hero is forced to move to its place continuously, so it looks like its paralyzed. If u use only the 12 locs.. you'd have to do 12 triggers x 6 per player...
Next, I have the AoE (area of effect) triggers... PER AoE trigger i'd need 12 detection triggers... so that's 12 x w/e the amount of AoE triggers I'll be willing to put in my map..
Right now I just need 3 per AoE triggers, as I create defilers under each player (player 1,2,3,4,5,6) locations, which should be centered at the hero they have chosen. This cuts down on the trigger WAYY better. Plus, it's always better to have player specific things.
Uhm, why not just 1 location per player and have 12 triggers (1 per hero) per player (72 total) that go like
P1: If Current Player brings at least 1 hydralisk to anywhere center P1 on hydralisk owned by Current Player
P2: If Current Player brings at least 1 marine to anywhere center P2 on marine owned by Current Player
... etc
Great.. now he's gotta do 6 triggers per spell... that's even worse than what Falkoner suggested..
Yeah, you can have "If current player bring at least 1 hero hydralisk to anywhere.. and if current player *casts spell 1* (w/e the condition may be... center location "hero hydra" to hydralisk owned by current player, create spell units (mutalisks) at "hero hydra" for current player.... but that's even more work than just having the triggers set in the beginning. and you get the same amount of locations that you need.
What I gave you is the easiest to work with... Look into Temple Siege.. The triggers are set to be the LEAST stenuous in terms of trigger number.
I did things such as using defilers as markers for AoE spells... using a universal DC for all spells and paralyzing and etc. ...
None.