It's taken me upwards of a year to get this. Tried it off and on with no luck. Finally figured out some secrets and that helped a lot. So here's a guide:
General:
You want to go to each building and drive the terror level up WITHOUT people leaving. This way you'll have as many chances as possible to make people jump out of windows and you can only do that when you have lots of people.
So drive this up by going to distant rooms from exits and spam something. Floating objects actually drive up the meter quite quickly.
To get people over the edge jumping, spam good objects right by the window the person is next to.
Specifics:
Kill the other ghosts as soon as you can. I don't REALLY think it matters but those are poart of your count so you'll be able to see the count more clearly.
Once your terror level is up, spam something BIG RIGHT NEXT to the windows. Look for objects with quick animations that you can rapid fire that have an X button feature. Those will make people scream the quickest.
I solved this by completing hospital...then half of theatre...then won it halfway through museum. Museum and Hospital give you the easiest jumpers.
Hospital:
- best window is upper right window. Best object: Wheelchair....move it all over the place and hit Y. It's a little slow but moving it around will get people as they come out of the left room.
Top left room has GREAT object...the shocker and the chair are really fast and scare people the most. Get them screaming with those and as they run out, hit em with the wheelchair.
- Middle left window: another good window...the Xraw and buzzy machine both can be spammed to get at least one jumper.
- middle right window. NOt a good window. People will run downstairs and out the door from here. ANd these objects stink.
WARNING: THere is a HUGE broken bug in this game. There is a little girl with black hair. If she gets scared in the basement and runs up those stairs, there is a glitch where she never makes it up the stairs and keeps repeating her movements. She will never be able to break out of this. Don't get caught in this. Otherwise your achievment quest is over.
Another warning: NEVER use ANY PHONE to scare people. Certain Phones when you hit Y cause the game to freeze and crash.
THEATRE:
Best windowws: Upper right and upper left. Well these are the only windows. This is a tough building.
Upper right window: Hard room. People approach from a slow ladder below. Once they are here there are 3 good objects that can be spammed. Although they aren't REALLY potent.
Hallway between the two windows gets people really scared. Use this hallway to get them screaming, then finish them with objects on either side.
Upper left: The bar is okay The tipping drink shelf by the window is perfect but a little slow. Still it got me a jumper.
Best object in the building: The organ! Spam it and they will instantly scream...however they will have to make their way up two ladders to jump out a window. THey are more likely to run out the front door but it's a good starter. The mirror in the green room is also great.
MUSEUM:
THIS PLACE IS AMAZING!
Great high windows. LOTS of great objects.
Only windows are on the third flooor in one big room. If you stick to this area you're pretty golden.
Great 3rd floor items:
Samurai - The best item in the room. He is right next to the left window. Run him around to quickly pump the terror level. FIre his weapon too. He can stand right by the window.
Ark - Show its light. It's in the middle of the room so can get people running toward the window.
Centurion (in red) - He can poke and grow. Another great one.
Busts - THey can fly around the room
Top Floor - A great place to get people screaming....Use the ship in a bottle to spam the storm. Great object
Middle Floor - The Drums, Zebra, and Bear are awesome. Bear especially. However people are just as likely to run downstairs...but using bear got me two people to become upstairs jumpers :)
Good luck. Keep at it. Stay by the windows and wait for people :)