I'm looking for all the gotchas surrounding trigger behavior and things that aren't intuitive.
For example, supposedly unit location data is not refreshed within a trigger cycle. I believe what this could mean is if I had 2 triggers like "X brings unit to location Y" and the first trigger removes "unit from anywhere", the second trigger will still fire off, even though that unit was removed. To get around this, I believe you can use death counters or switches to explicitly communicate this information.
Are there other gotchas that are important when building complex trigger systems?
None.
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For example, supposedly unit location data is not refreshed within a trigger cycle. I believe what this could mean is if I had 2 triggers like "X brings unit to location Y" and the first trigger removes "unit from anywhere", the second trigger will still fire off, even though that unit was removed. To get around this, I believe you can use death counters or switches to explicitly communicate this information.
This scenario actually isn't an issue and doesn't happen the way you're describing. Remove unit immediately updates that data so if you check for the unit right after, it won't be detected. On the other hand
kill unit will mess things up because it's more of a "sentence unit to die" order and that unit will continue to exist for the rest of the trigger cycle. The link Oh_Man posted helps with many of the quirks and nuances, but to be honest, I think there are more than just that. It's unfortunately usually hard to think of/remember them until you encounter them in practice though.
The page Oh_Man linked is a goody, I think the main all-articles page also is a good reference:
http://www.staredit.net/wiki/index.php?title=Special:AllPagesIn particular, there are articles on the Bring and Command condition bugs, an article on Triggers themselves and the very specific order in which they run, and Wait blocks. There are definitely other problems like Ultraviolet mentioned with the Kill action, and for instance another I think I remember are there are a handful of units you can't actually spawn with triggers (have to have them pre-placed on the map, like one of the hero templar units), but I don't know of a central resource that lists everything.
None.
I think I remember are there are a handful of units you can't actually spawn with triggers (have to have them pre-placed on the map, like one of the hero templar units)
This one is fixable these days thankfully. You can do it with EUDs by changing the StarEdit tab in units.dat. I think it's the location triggers and non-location triggers boxes. I always just make that section the same as it is for normal units for any unit I want to be creatable with triggers.
