UDK Basics

Hello UDK

Space - Switch between Translate, Rotate, and Scale manipulator widget modes.
` (to the left of the number row) - Switch between World and Local coordinates.
Ctrl+S dumb - Does not save. This does a geometry subtraction with the brush.
Ctrl+A dumb - Does not select all. This does a geometry addition with the brush.
F4 - With an actor selected, brings up its Properties window.
Ctrl+D - Duplicate. This creates a copy which is slightly offset in space.
Ctrl+C Ctrl+V - Copy/Paste. Doing this creates a copy which is not offset from the original.

Hidden functions will show up when you right click many of the buttons around UDK.

Additionally, a treasure trove of options will show up when you right click an Actor in the Editor Window. See the Properties Window section.

Left Click + Move - Rotate the view left and right
Right Click + Move - Freely spin the view around
WASD - Fly in 3d space (also Numpad 8/4/2/6)
QE - Fly up and down in 3d space (also Numpad 7/9)
Right Click + WASDQE important - Fly while looking around - a.k.a. the way you want to be moving
Scroll Wheel - Speed up and slow down while flying

Most of these are for that “wtf did I just press” moment:

I - Crazy glowy fog mode
O - Hide all wireframe volumes
F - Show/hide world fog
Alt+W - Show/hide static meshes
G - Game mode - Hides all 2d sprite actors (lights, etc) which will be invisible in game
H - Hide selected - Undo with Ctrl+H or the eye with an X in section 14
Alt+G/H/J - Change viewport to top/front/side orthographic mode
Alt+F - Change viewport to perspective mode
Z - Do a weird telescope zoom out (also Numpad 1)
C - Do a weird telescope zoom in (also Numpad 3)
B - Show/hide CSG brush
1 - Center viewport on 0,0,0
Numpad + / Home - Center viewport on active object
Alt+Number Row - Change viewport render mode