Re: Action to command the servant?
Anyone know an official source indicating that you need to use a standard action to command the servant? Otherwise, I think it's up to house rule.
In that case, my provisional house rule is as follows:
Actions: The servant does not have its own actions. Instead, its owner spends actions to have the servant take actions. The owner can specify whether the servant should continue doing the same action in subsequent rounds. If the owner so specifies, these repeated, subsequent actions do not require the owner to spend more actions and the servant mindlessly continues performing the same action until given new commands. For example, the owner may have the servant pick up an object as a minor action, have the servant move the owner's speed as a move action, or continuously follow the owner with one initial move action.
This house rules mirrors many of the similar rules governing pets, familiars, etc. -- i.e. the owner spends an action to have the companion do something. It keeps the servant useful and low maintenance but prevents getting completely "free" actions for the owner. It also allows for humorous mistakes when the owner forgets to tell the servant to stop doing something, e.g. the brooms in Disney's Sorcerer's Apprentice.
It's still not 100% clear how to command the servant but I think I'm going to interpret it as needing a verbal command.
Re: Passing through doors, etc.?
The conjuration rules explicitly prohibit passing through blocking terrain.
Re: Enemies attacking the servant?
The conjuration rules explicitly state that conjurations can't generally be attacked but when they are, that they use the owner's defenses. As example, I would say if the owner's enemies attack the servant because it's closing the door they want open, then they're out of luck. However, if they want to attack the lantern being carried by the servant they can make an attack vs. the owner's defenses.