…How to win at Rock Paper Scissors.

The last four at the best:

4 - Telegraph Your Throw
 Tell your opponent what you are going to throw and then
actually throw what you said. Why? As long as you are not playing
someone who actually thinks you are bold enough to telegraph your throw
and then actually deliver it, you can eliminate the throw that beats
the throw you are telegraphing. So, if you announce rock, your opponent
won’t play paper which means coming out with that scissors will give
you at worst a stalemate and at best the win.
5 - Step Ahead Thinking
 Don’t know what to do for your next throw? Try playing the
throw that would have lost to your opponents last throw? Sounds weird
but it works more often than not, why? Inexperienced (or flustered)
players will often subconsciously deliver the throw that beat their
last one. Therefore, if your opponent played paper, they will very
often play Scissors, so you go Rock. This is a good tactic in a
stalemate situation or when your opponent lost their last game. It is
not as successful after a player has won the last game as they are
generally in a more confident state of mind which causes them to be
more active in choosing their next throw.
6 - Suggest A Throw
 When playing against someone who asks you to remind them about
the rules, take the opportunity to subtly “suggest a throw” as you
explain to them by physically showing them the throw you want them to
play. ie “Paper beats Rock, Rock beats scissors (show scissors),
Scissors (show scissors again) beats paper.” Believe it or not, when
people are not paying attention their subconscious mind will often
accept your “suggestion”. A very similar technique is used by magicians
to get someone to take a specific card from the deck.
7 - When All Else Fails Go With Paper
 Haven’t a clue what to throw next? Then go with Paper. Why?
Statistically, in competition play, it has been observed that scissors
is thrown the least often. Specifically, it gets delivered 29.6% of the
time, so it slightly under-indexes against the expected average of
33.33% by 3.73%. Obviously, knowing this only gives you a slight
advantage, but in a situation where you just don’t know what to do,
even a slight edge is better than none at all.
8 - The Rounder’s Ploy
 This technique falls into more of a ‘cheating’ category, but
if you have no honour and can live with yourself the next day, you can
use it to get an edge. The way it works is when you suggest a game with
someone, make no mention of the number of rounds you are going to play.
Play the first match and if you win, take it is as a win. If you lose,
without missing a beat start playing the ‘next’ round on the assumption
that it was a best 2 out of 3. No doubt you will hear protests from
your opponent but stay firm and remind them that ‘no one plays best of
one for a kind of decision that you two are making’. No this devious
technique won’t guarantee you the win, but it will give you a chance to
battle back to even and start again.

Source: http://www.mentalfloss.com/blogs/archives/2032

Found at: http://www.dumblittleman.com/2007/04/how-to-win-at-rocks-paper-scissors.html

Also see: http://www.freakonomics.com/blog/2006/07/26/annie-duke-wins-2nd-annual-world-series-of-poker-rock-paper-scissors-tournament-my-research-assistant-gets-knocked-out-in-the-first-round/