Best way to short the DJIA to be down 20% by Dec 2013?

My dad said to buy a put on the dow, and this pops up when I do a search for that:

http://answers.yahoo.com/question/index?qid=20081001102206AABVv4I

but this pops up when I search for how to short the DJIA:

http://www.ehow.com/way_5905296_dow-jones-short-strategies.html

Drops 20% of what? Current levels or whatever it is heading into Dec 2013? Don't you have to predict a level that you want to buy puts at?

Buy Jan 2014 DIA puts? Maybe do a put spread, buy the 105s and sell a lower strike (like the 80s) to mitigate your premium a bit.

http://finance.yahoo.com/q/op?s=DIA&m=2014-01

J'14 P at whatever 20% less than the close today is? A spread would probably be better but if not then a simple put is probably the best way.

What's your time until target?

thanks for replies so far, just want to keep it really simple and as low cost. I'm putting my money where my mouth is in saying that the DJIA is heavily overvalued, to the tune of 20%. By December 2013, and im not looking to unload before then, it will have dropped that much. I want a fixed risk way of capitalising on this. Im assuming I want some european puts on the DJIA expiring near to Dec 2013, or shortly after, not before). If anyone has a smarter way of doing this, do chime in.