In honor of the first day of December, a few words on a subject near to my heart (or to my chilly feet and fingers, anyhow):
One of the persistent errors of cheap genre fantasy (along with horses that are really motorcycles and ships that have late 19th-century rigging and construction in an early-medieval environment) is a complete unawareness of how complicated a process heating with wood actually is. The way fantasy characters build and light fires in the mere blink of a subordinate clause, you’d think they were using gas logs or an electric space heater. What’s worse, once the fire is going nobody pays it a bit of attention thereafter.
Well, the first twelve years we lived in our current house, we heated it by means of a wood-burning furnace lurking like Moloch down in the basement, and I can tell you from experience that it doesn’t work that way. Even with the aid of matches and butane-powered firestarters and similar modern innovations, building a fire is still a fiddly process, involving a lot of messing around with tinder and kindling and carefully putting two or three bigger sticks on top of the resulting tiny blaze — which just went out, so you have to start over with the tinder and kindling and then the two or three bigger sticks again — and then you have to keep the smaller sticks going until the bigger ones catch fire, and then you can start putting on some serious logs and if you’re careful and put the structure together right the first time the logs won’t crush the whole thing and snuff it out — and God help you if you’ve got wet or green wood, because then the whole process is going to take twice as long and put out only half as much heat.
And once the fire’s actually going you have to keep feeding it more logs at regular intervals, and — especially in an open fireplace — keep rearranging the logs so that they’ll burn better, not to mention periodically clearing out the ashes. (Which in a pre-modern society would be saved for soapmaking and other uses, but which these days are a pure nuisance to get rid of.)
A wizard with a reliable fire-starting spell could probably eat for free at any kitchen table in the kingdom. Especially if he had a reliable flea-and-bedbug-eradicator in his other pocket.
Dr. Doyle's Blog 
Oh, my goodness, you’ve reminded me of my SCA days. I was taught how to use flint and a striking iron and patches to light the tinder. Fiddly is an understatement! And, if you’re not dealing with an enclosed furnace, you’ve got the direction of the wind to worry about, too, and sitting upwind of the smoke. I am so going to have my soldiers on the Peninsula have to deal with all of that hassle. (Though they can use an unloaded firearm to do the striking, at least.)
I ran into that ships problem recently — luckily while the story was still in manuscript stage. A knowledgable friend pointed out that I’d completely blown the difference between a 19th-century tall ship and a Barbary pirate galley. It only wound up shifting about four details, maybe eight sentences — removing “companion-ladder”, changing an incidental character from a sailing-master to a pilot, removing a reference to the deck and putting one in about the oars — but it made all the difference to the reader who KNEW! Whereas, to a reader who doesn’t know, I’m suspecting they’ll still go “Right. They’re on a ship,” and move on to the Naughty Bits, which are the main focus of the story anyway.
There’s one of the primitive tech guys on YouTube, down in tropical Australia, who does a lot of stuff with firing ceramics, and every time he goes through several step go ’round with a fire drill (which he does without a bow– he did it a few times that way but decided it was easier just to spin it with his hands directly), and a wad of plant-fluff tinder, and then some dry leaves, and then under his not too carefully laid fire, but then he doesn’t have the tools to use split firewood. When I grill I work with newspaper tinder, and then work up from twigs to small sticks in a crisscross fire before laying the charcoal on. Even just sitting outside under cover, the paper can pick up enough moisture to make it resistant to lighting.