Use the spellings of the wire colour.
The BLue goes on the left, the BRown on the right.
Green (if it has it, so many don't nowadays) is alone at the top.

First 2 letters of BLue = B L (Blue Left)
First 2 letters of BRown = B R (Brown Right)
(Mensa Reject has gone out, I'll be back on, Fri 16 Jul 2010, 2:17, 1 reply)

Does it make any difference with AC?
I'd thought that as long as you don't miix the earth with either of the others, then it'd be fine. Certainly worked out fine for me in Switzerland with their odd wiring schemes on the older plugs...
( Colonel Boris "...a desperate Buzzfeed imitation...", Fri 16 Jul 2010, 3:25, closed)

Yes, it does
Even though it's AC, the neutral line is tied to earth potential (although over long cable runs, some voltage can build up). The live then alternates + and - from the earth point. Most switches work in single pole mode, i.e. breaking the live line only.

If you swap the live and neutral, then you'll be breaking only the neutral line, so the equipment is effectively still live. It won't work because there's no circuit, but were you to rummage around inside, you'd be liable to get a shock.
( K2k6 has a proper job these days, Fri 16 Jul 2010, 8:30, closed)