In a newspaper, in a damp free location. Whatever you put them in make sure that the tubers are able to breathe and wrap them in a newspaper for the winter warmth !

I grow dahlia many years ago for show but now just a hobby - cut down the stems to about 4-6inches - stand upside down to drain for a few days as the stems are hollow and hold moisture- you can remove the smaller tubers from the main stem as long as it has an eye at the end near the stem as this will produce the new shoot next season - store in sand or peat Damp NOT wet to stop them from rotting. I store mine in bread trays then cover them with Black plastic bin liners stretched over the top of the trays and then stack them on top of each other this allows air to pass through but keeps the frost off them - Keep them in the green house or in the garage -The eyes begin to swell quickly, typically within 4 to 8 days after the plant is destroyed by frost or being cut down. If you wish to divide the tubers when eyes are optimally visible, you should dig and divide the tubers in that 4 to 8 day window do not store them dry as they may dryout - and remember to mark them with the name of the dahlia in each box - good luck Ken

http://www.gardenersworld.com/how-to/projects/creative-projects/how-to-lift-and-store-dahlias/99.html

The above is link to Gardeners World website, a video on how to store Dahlia using the Newspaper method, it is highly recommended that the Tubers are dry and drained of moisture before storing in frost free condition.

http://www.growsonyou.com/scrumpygraham/blog/13412-the-dahlia-season

That's all you need to do. No need to bother with newspaper.

I found the News of the World the best paper to use lol

I found News of the World the best paper to use

I dont want to make this into a confusion but this is the best I found that to dig tubers out, wash them and lay in paper, NEWS Paper or even a tissue to store them as it will help keep the moisture away.
Scrumpygraham's method is Ok if you are thinking of growing cuttings otherwise your tubers are going to go to hell guaranteed. Why would you keep a tuber wet, I have bought so many bulbs and tubers from garden centers never once I have seen the bag wet,the professionals take utmost care to keep them dry by adding fine wood chippings, making holes in the plastic bags etc
KenBosor's idea is from many years ago which he himself says so If you want to try at your own risk and close them in a black bin liner which has no room to breathe all the moisture is going to be in the bag, which will make the temperatures to rise in the bag and microbes will get to work and eat your tuber.
Iciar needs to own a garden and do some gardening first to able to read the News of the World in it let alone give advice !!!

Um, I suggest you go to specsavers ASAP. Where on earth does it say store wet?
My method is based on 30 years growing them and having tried all other methods including the news of the world.
Newspaper doesn't keep moisture away. The converse is true. If your tubers are not bone dry then water from them goes into the paper and you end up with a right mess.
Haven't lost a tuber in years doing it my way. I did using other methods.
People must believe what they want but I certainly wouldn't take any advice from someone who can't read.

Scrumy's wet dreams are not damp, he he he.
Yeh seriously Gardeners World is wrong !
Just read the question the person has asked how to store not to grow them Inside.
If you going to put bulb,seed or a tuber in soil your way it will start to shed root and When you plant them outside in spring you will create root disturbance which tubers dont appreciate much, there are lots of fine hair roots that feed the tuber.in your own blog tubers are sprouting in your storage trays which means theyve been active while we want them to conserve energy while in storage.
So you are creating a hypothetical situation that people will just not store them dry ?
Seriously mate were you really thinking anyones giving you advice, if you can go visit the Dreams bed shop and get a decent bed to properly dream at night otherwise your day dreaming is taking you ashtray !

What on earth was all that gobbledygook from Indian.
I'm sure in his dream world that makes sense but again, people must learn to read before posting drivel.

"in your own blog tubers are sprouting in your storage trays which means theyve been active while we want them to conserve energy while in storage"

Um, no, they were deliberatley started off into growth, hence the sprouting.

Anyway, as some people can't grasp the art of reading, here's a video link from the true professionals

http://www.youtube.com/watch?v=hfRhty53LNU&list=UU9W_0LqMAr2C6zoTSSgeC3w