or use the arrows, Q (down) and E (up) instead

(Q and E only for TAB mode - In play cam, Q is "Quit game")
also, if you forgot to put the walls up, you can use the "home" and "end" buttons.
For going up/down floors, use the "page up/down" buttons.
. and
, is rotate camera (play mode)
+ and - is zoom in and out (but you can also use the mouse wheel for this)
And you can tilt and move the camera around with either moving the mouse, or using the touch pad on a laptop (TAB mode)
C is shortcut for taking pictures
P is pause/start.
1, 2, 3 is normal, faster, and very fast game speed
CTRL in combination with 4 to 9 saves camera settings (you can save one set for free cam (TAB), and one set for normal camera mode)
Also,
showheadlines on/off turns on/off speach bubbles and most of the other pop up text bubbles and such.
also, if you don't have a clue on how to get the gridlines away when photoshooting in buy/build mode, either press the recolor button, or the shortcut R just before going into Free cam mode. This is the fastest and easiest way of removing them.