They are an important tool to any scout. They provide heat, light,

Yeah, yeah, we just build them 'cause we like to watch things burn. All those useful things are nice side effects. Anyways, fire types, construction methods, and reccommended amount of wood.

Type Construction Amounts of wood needed
Tepee Set up one tepee. Soak with kerosene. Light. 6-20 large poles, one teepee covering, 5-20 gallons of kerosene. Just kidding!
Real Tepee Fire Lay smallest sticks in a pile, making sure not to compress or crush them. When pile is about 1 inch high, make nest, place tinder in nest, partially cover with more smallest twigs. Leave part of tinder open for ignition and ventilation. Gradually increase size of twigs placed on top of the pile untill you are putting on sticks slightly smaller than a pencil. Next, put same-size kindling (about pencil size) around the sides, making sure to leave space for ventilation. These sticks are suposed to keep the fire upright and burning untill the larger support logs catch. After you have an outside pencil-stick covering where the sticks are almost touching each other at the top, you build the teepee frame. Large sticks, much smaller than your wrist but bigger than your thumb, should be used to construct a tepee. The log base should be close to, but not touching, the pile of kindling. If it's more than an inch away, it's too far. Use larger sticks on the very bottom, with the stick size decreasing slowly as hight increases. You should have at least 6 sticks suporting your tepee. Don't forget to leave the side with the tinder open for ventilation! Once about 2/3 to 3/4 of the support sticks are covered in small/medium sticks, use taller sticks on the sides if you want. These should be larger than a pencil but smaller than your thumb. Make sure you have more tinder, kindling, and fuelwood on hand because this fire will burn out very quickly. As soon as flames are big enough to handle more wood, carefully put on some more kindling. Keep feeding the fire, and once the support wood burns, the fire is big enough for small logs. 6-8 larger-than-thumb strong sticks for support
Approx. 2-3 hatfulls of tinder
3 hatfulls of kindling
A large amount of larger kindling long enough to not fit into a hat
approx. 5 small logs and 3 large logs should be on hand before lighting this fire. 10+ large logs should be enough to keep it going through the night.

Cabin Fire First, this will require kerosene to make it look/act like OA fires. There's a reason Kerosene is called OA Juice. Second, to make it work without kerosene requires a stunning amount of kindling.
Start by building the base from the tepee (above). Put a log tower above it, but leave the back open. You'll need to cut some of the logs special. After the tower is at the level of your tinder pile, make a "shelf" of interlocking branches about halfway accross. Loosly pile tinder on that. On top of the tinder, put small kindling. Put more logs upwards, this time in a square, decreasing in size slightly. After the log cabin is as high as you want, build a tepee of mid-size sticks in the middle. Fill with kindling. a few logs up from that, build another cone of mid-size sticks, making sure not to compact anything so that air and fire can go through easily. Cover this cone with kindling.
If you want to get fancy, you can skip a log here and there to provide superior airflow. Light at the bottom. The bigger the ignition source, the better. If you just HAPPEN to have a powerfull windproof lighter, USE IT! If you have a flame thrower, USE THAT!
Another tip: It might help to set some newspaper on fire near the top to start the draft going.
10-35 logs
As much tinder and kindling as you can get
Kerosene or some other firestarters will help.