What is the best way for long term water storage and water purification in the field?

[Cinaet]

Here's a low-tech way to purify water using sunlight.

http://www.ehow.com/how_6371825_purify-water-using-natural-resources.html

I have a couple of shiny metal trays on top of a cabinet in the garage (they started out life as the trays to catch poo in the chicken and rabbit hutches), several 2-liter pop bottles and a stack of old cotton t-shirts (for filtering dirty water) I've saved specifically for this purpose. I've also got a gallon of Clorox bleach up there.

Lurker's right ... boiled water tastes like arse ... but intestinal upset from drinking bad water (which I've had btw) is a bazillon times worse ...

This is my favorite solution. It's cheap enough that anyone can do it. There's very little effort involved. And it's a proven technique. It doesn't have to be your only way to sanitize water but it really should be on everyone's list for preparedness.