What would you think if the pilots of a plane in which you are travelling go out of the cockpit leaving the thing flying for itself while they go to chat with a stewardess? Any good autopilot can fly on its own but would you fly safe? Then why should anybody feel safe when a campfire is left at its own devices?
Forest fires are terrible things not only for the wholesale destruction that they generate, the money they cost to fight, the human and animal toll in lives, the destruction of whole ecosystems and damages that easily last for decades. In this sense, they are as damaging as catastrophes or disasters as any solid aircraft accident, if not more. But as we said, they are not terrible just for all this but because it is far harder to escape and survive any of them than most people think: Forest fire can move at a pace that could easily overrun any backpacker and in some cases, even vehicles. Forest fires begin as very small things and even minute embers from an unsupervised campfire could be as destructive as some major napalm bombing on your forest of choice. Thus, no fire should be left to its own devices even if it looks like that everything is okay. So always respect these rules:
Never start a campfire when such a thing is prohibited or disallowed: Not only you should not act against the law, but consider that if someone took the bother to put in place such a rule it is reasonable to assume that the costs of previous fires and the difficulties involved in terminating them would probably justify acting prudently.
Don't initiate a campfire in areas or places where it could easily propagate: A fire could become incontrollable after thirty seconds since it is initiated; indeed, making a fire too near combustibles or flammable materials increase both the odds of an accident happening as well as the speed at which it would propagate.
Never leave any campfire unattended, not even for five minutes: Considering the speed of propagation described in the rule above, it is easy to understand why the supervisor of a campfire should never leave it alone or go too far a way. If you cannot reach the fireplace back in less than thirty seconds, then you shouldn't be there.
Never leave a fire to quell off for itself, even if it looks like it has already died: Make yourself positively sure that no flames or embers remain before leaving. Destruction, victims and quite likely, legal fees would cost you far more than five minutes of your time.
Don't think that bad weather will put off the fire that you forget to extinguish: Even if bad weather is above and heavy snow or rain is falling, there is really no way to assure that a propagating fire could die before it causes some major damage. Forecasting is just playing with odds instead of certainty and thus, assuming that the weather could play a role in something that is required for certain would be a gross mistake.
It is easy to forget that a campfire is not your regular kitchen oven back at home. It would be unwise to leave something over the fire at your place - many home fires start in kitchens - but in a camp the dangers multiply because flammability conditions are usually much higher. The person left in charge of a campfire should not be assigned other duties that could potentially put him too far away from the fireplace or in a condition in which he could not pay attention and supervise it. Loss of eye contact with the fire is the most common mistake but getting too far away, even if the fire remains visible, could also spell disaster because if flames start propagating it might well be difficult or impossible to return in time to put them off safely. Thus, things like going to collect water to a nearby source should be left to others and the person in charge of the fire should be limited to doing things like drying up clothes around the fire, making some repairs, preparing dinner and so on. A pilot might look at the passing landscape or drink mate as the autopilot takes care of the flight, but he should never leave the cockpit alone while that is going on.
Cooking outdoors means not leaving the fireplace even if the weather is bad.