1. usually refill during the summer when the 20lb tank is good and warm. If I have to refill during the winter, I'll keep the 20lb tank in the house overnight to warm it.
2. only refill outdoors (not in an enclosed area)
3. avoid being anywhere near a flame source
4. keep empty bottles in freezer overnight before filling
5. keep track of the number of times that I refill a tank by labeling it and refill a max of 5 times (I use to refill more, but had a few seals start to leak)
6. keep the recently refilled tanks outdoors for a few hours and smell for leaks before replacing the plastic cap and storing in my garage
Because of some concern I've heard from others about possibly transferring particles/junk from the 20lb tank to the 1lb tank, I only use the refilled tanks for my portable heater and only use new tanks with my auger.
Side note: my wife typically shows her ignorance by saying something is "stupid" when she doesn't understand it.
link to one horrible occurance. http://minnesota.cbslocal.com/2012/02/06/1-dead-1-injured-in-polk-county-garage-explosion/