On Agent, you only have to save 2 hostages, the rest can die. I'm not sure about the numbers on SA and PA, but they can be easily figured out.
The guards won't start executing their hostages until the door to their room is opened. Thus, we open the door and leave so they kill them. There's one exception to this - The 2nd floor room on the right. You have to actually see them before they start their execution.
If the hostage objective completes just before you get the RCP-120, Carrington can build up a large queue of lines he has to say. He says a new line for each objective. You want it so he starts a new line as you're uplinking "Things are desperate...". If he doesn't say it then, he says it after the ship has already blown up, then runs through the rest of his lines wasting 10 seconds or so. This is why breaking the glass on PA wouldn't help, because you'd have to wait for his lines.
You'll notice both the A and PA WR strats involve having the hostages complete while upstairs. This gives Carrington plenty of time to say his RCP120 line before you get there, so his queue is smaller.
For PA (WR strat), the hostages complete very rarely. From memory it's about twice an hour. The 53 A strat is ok, but you need them to complete earlyish in the firing range. 52 A involves aiming the grenade perfectly, other than that it's fine. SA can be a bitch, you need a hostage (or two?) in the firing range to actually live.
