Something basic like getting a spirit to watch a door should have best-practices. Security organizations probably have this stuff spelled out precisely to reduce unwanted variation in spirit behavior.
In the best practices for
WHOM ? The person who is giving the orders? Or the person who has to follow them? Remember, they are two separate individuals, with separate ideals, wants, desires, and possibly opposite objectives!
Remember nothing is cut and dried, heck if it was, these forums wouldn't be here
And the Law profession would be out of work. Interpretation is key, and subjective to the individual who hears the commands, and can be twisted and warped as suits that individual - this is what your spirit index helps to measure.
If you have a really crappy Spirit Index, expect your Spirits to twist and warp every command to their best advantage - you have proven that you are NOT their ally after all.
However, if your Spirit Index is good, then spirits are going to be more inclined to interpret your orders in a favorable way - because you HAVE proven to be an friend of spirits.
Security organizations DO run into these problems, that is why spirits are not the sum total of a Corp's magical defenses. In many ways, a Spirit is no more effective then an average security guard - just for a different plane. They still have to spot the target (its not automatic, yes sneaking skills works on Spirits), they still have to engage the target - or whatever their protocol is. Which is no faster then the DNI voice coms a security guard is going to be using. The Bio monitor will tell someone he is gone, just as fast as the mage knows his spirit is gone... And really, the Guard is more effective in that regard, as usually it's the Security Command that gets the alert when a guard goes down, where the mage has to rely that info to someone else (as an astrally projecting mage is actually really combat ineffective on meat targets.)
More importantly, have you ever tried?