For the usual light fixtures -- wall lights and ceiling lights -- the wires are usually easy to hide.  Holes are drilled through boards and channels are made to hide the wires.

The same thing can be done with table lamps, but what about the times when there isn't a piece of furniture to hide where the wire enters the wall?  In the guest room, I had just this situation; the table next to the bed had a thin base.  I could have pulled the wire behind the bed and hid it there, but where's the fun in that?  :D

So, I decided to make a mock outlet.  First, I slipped a white bead onto the lamp wire; this will mimic a plug.

I cut a channel in the wall behind the table to feed the wire up the wall and through the ceiling (eventually, when the ceiling is put on).

I cut a small hole in the wallpaper where I want my outlet to be, making sure it was in line with the wire channel.

I used a small piece of bass wood painted gloss white to mimic the outlet cover.  For the "open" outlet, I drew on the outline, indented it a bit with an X-Acto knife and then brushed a bit more paint over the drawing.  On the other side, I made a hole to feed the lamp wire through.

I slipped the outlet onto the wire behind the bead and then fed the wire through the hole in the wallpaper.

I determined the length of cord I wanted and taped the wire into the channel in the wall.

I glued the wallpaper in place, glued the outlet in position on the wall and then moved the bead to sit flush against the outlet cover.