Whenever possible hide behind walls, or in doorways if you are about to be spotted by a searchlight, as lying down or doing a roll isn't always effective.
When placing your men around the top of the building, put them all on the same side, the best side is the bottom one. Now press 'F1' which will show you the side where your men are placed. Scan the top windows first for an empty room. You should see the men dangling from ropes, if not then you have got the wrong side fool!
You should send your first man in on the top floor. If all the windows have silhouettes, the hostages are the one's with a slightly fatter silhouette at the window than the terrorist's silhouette. If you shoot a hostage at the window by mistake, you might as well start again, don't forget there are only 3 hostages!
When your first man has entered a window on the top floor, clean the top floor of all terrorists (in green, hostages are blue - they also don't move around much) When you have killed your first terrorist, position gun where he once stood, so when you burst in on the next one, you don't have to mess about positioning your gun, but can shoot him straight away.
When top floor is clear move your man to the top right room, (the one with only one door) & stand him in that room with his back to the door. That way, when you have a hostage you can take him to this safe room, and leave him, as any terrorists can't get in through the door because one of your men is protecting the door, but you can still get in and out.
Now bring another man in through the top floor, still leaving one man in the top right room protecting hostages you leave there. Now go forth and find them their hostages. If there is a terrorist, with a hostage behind him. DON'T shoot the terrorist as you will kill the hostage. Instead run straight into the room and straight at the hostage/terrorist, so you and them occupy the same space. Don't stop, keep holding forward & you should be on the other side of the room, as the hostage follows you, the terrorist doesn't. BUT, doing this you have to be very QUICK.
Now take the hostage to the top floor, the top right room, where your 1st man is on guard. Walk into this room and back out again, the hostage will stay there. Now you are free to go & get another one. Once all hostages have been successfully rescued, Game over !