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.

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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.

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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.

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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.