forestwalker
Bushcrafter (boy, I've got a lot to say!)
When I was in the far north we always carried a water bottle and put a bit of water into the bottom first before trying to add any snow.
This also utilizes the fact that heat transfer from the pot to the water is much, much more efficient than from pot to snow.
The old timers said that if the billy was real hot and snow as add to it, that it would impart a scorched taste to the water. I always added some water first so I can't say if this is a fact or just some old campers tale.
Another hint is using a lid whenever possible. Saves on smoke, ash, etc getting into your water and mucking it up.