Damaging units through triggers?

Okay, for one, I've tried searching for this, I know it's been asked before, but I can't find it anywhere so I'm making a new topic about it.

Anyway, I'm working on some custom spells, and I'm just wondering, how am I supposed to do damage to units through triggers? I know there's something I'm obviously missing, but I've tried looking through the triggers and I can't find any triggers that take damage off of units. How can I make this work?

I think its action arithmetech (sp?) and then like

Life Of UNIT = Life of UNIT (minus) DAMAGE

Unit - Set life of (unit) to (Life of (unit)+ or - or / #)

or

Unit - Set life of (unit) to %

Try to avoid damaging units this way, because you don't get gold and experiance. There are damage spells for just anything, so use them with no model as dummies.

blah.... if the said units life will become lower then 1, set it to 1.

then have a playerowned unit (shade or w/e) with like 1000000 range just do a simple 100 dmg attack on the said unit.

Better Yet, if the said unit is supposed to take an Exact amount of dmg (or random) dont do "Set UNIT = Unit - X" just create an invisable unit and order it to attack the targeted unit.

This might mean you have to have tons of units, but it still works.

the real trick is to have a modified flying goblin land mine Unit with a modified Aoe Damage upon death that has an aoe of 1 an a damage of 1000, give it the Cinematic arthas model (wich is in fact no model) , then after setting the life to 1 create that mine at the position of the unit that has to be damaged, after that kill last created unit, and done

vex has a good idea there but basically if you do damage through triggers you will get no bounty or exp. i always always base my spells off of spells that do the damage and than add my special effects through triggers. like if you want an arrow to shoot and explode base it off flame strike than use triggers to make the arrow.

the only exception to this is if you do damage based off a % of that units life. because you can never actually kill a unit by removing 50% of his life. no matter how many times you cast it it will only lower his life 50%.