Mirror an Object in Blender

While I was playing with character modeling I needed to duplicate and mirror an object. I quickly googled around and found the following:

SHIFT-D
SX
ENTER

OK. I tried. Nothing happened apart from the duplication. It took me a while until I noticed I actually have to move the object after SX.

I made a series of screenshots about this:

This is the default scene in Blender:

Put your 3d cursor where you want to have the mirror:

I modify the default cube a bit to demonstrate the mirroring.
We will move the upper right vertex a bit:

Here is the modified cube:

Change the pivot to the 3D cursor:

In object mode select the object. Type:

SHIFT-D
SX
-1
ENTER

Instead of typing -1 you can just move the object, but blender will scale it X size.

Here is the result: