Thanks to Red Dawg NY, a very devoted SimTower fan, I now know how this cheat works:
1. Save your tower on a floppy disk.
2. Go to a DOS prompt.
3. Type the following, in this order:
A: (press enter)
Dir (press enter)
Debug towername.tdt (press enter)
e 100 00 24 ** 00 85 FF FF 00 (press enter)
REPLACE ** WITH THE NUMBER OF STARS THAT YOU WANT YOUR TOWER TO HAVE. 01 IS ONE STAR, 06 IS "TOWER" LEVEL.
w (press enter)
q (press enter)
4. Exit DOS and reload your tower. You will have the desired number of stars, plus a whole lot of cash!
DOUBLE YOUR STARTING FUNDS:
Start a new tower. Before you do anything, place a section of lobby in the far left corner on the B9 level.
RESTRICTION: In some versions of SimTower, if you want to do the 2 or 3-Story Lobby cheat as well as this one, you must hold down SHIFT+CTRL when placing the section of lobby.
2 OR 3-STORY LOBBY:
When placing the first section of lobby on floor 1, hold down SHIFT for a 2-story lobby, and SHIFT+CTRL for a 3-story lobby.
RESTRICTION: This cheat only works with the ground lobby, not the skylobbies.
FANCY STAIRS/ESCALATORS:
First build a 2 or 3-story lobby. Fill the floor above it with fast food and offices. Then build a staircase on floor 1 going up towards floor 2. When you reach the 3 star rating, put some restaurants and shops on that floor and build an escalator in the same way.
GUARANTEED TREASURE:
As soon as you build your groundlobby, do the following:
1. Build an elevator at about the center of the lobby. It doesn't have to be perfect.
2. Drag the elevator down to B3.
3. Build a fast food place on each side of the elevator.
4. It is guaranteed you will find buried treasure.