Toolset Controls
General

Right-click toggles between Select/Paint for objects and terrains.

Object Manipulation (Creatures, Placeables, Effects and Trees)

To move an object on the X/Y: Directional arrows (or Alt+Arrows)

To rotate objects: (Can't rotate trees)

    Mouse: Select the object(s) then hold down shift + right click drag
    Keyboard: Ctrl+Left/Right Arrow

Raising and lowering objects:

    Mouse: holding down alt while moving the mouse forward and backward quickly raises/lowers an object
    Mouse (precision): Shift + Mousewheel
    Keyboard (precision): PageUp/PageDown

To make an object stack atop another placeable, hold down "S" while placing it.

To drop an object to the ground, press Space

To hold a placeable in place without actually placing it, hold down CTRL

To lock a placeable into an x-y position: "L"

To lock a placeable into a z position (height): "Z"

Camera Controls

Panning - movement of the camera on the x/y plane: Hold (Control + Left mouse) and drag

Rotate the camera: hold Control + right mouse and drag

Rotate the camera: press middle mouse button or wheel and drag

Adjusting the camera height: Ctrl + Shift + Vertical Mouse Movement

Zoom in/out: roll mouse wheel

Interior Tile Placement

Rotate tiles: Left & Right arrow keys

Switch between tile variants: Up and Down

Copy a tile: with a tile selected, Right-mouse will copy it

Credit goes to Grinning Fool from the Bioware boards