Pretty much what everyone else has said: bandana and then filter or chemicals. For me it would be bandana and Aquamira drops. I carry a lot of bandanas, usually one for every day on the trail (one never knows what they'll be used for <img src="/forums/images/graemlins/grin.gif" alt="" />) so I could strain the water a couple of times before treating it.

I've got to remember to catch rain water!
_________________________
Why am I online instead of hiking?