My standard operating procedure was to catch clear fast running water in my bottle, drop in a Micropur tab and wait 30 minutes. Clear fast and running isn't always an option.
I think that I've been lucky up to this point to have suffered no ill effects.
I am moving to a gravity flow filter for the large baddies and adding the Micropur tab afterwards. I plan on using the same wait time of 30 minutes.
Party On ! 2010