Can be built completely from scratch with materials that you can find in the woods. So for this one you need to find two trees that are about as wide apart as you are long. This is going to be the base from which you build your shelter so make sure that the entrance is facing away from the direction of the wind/weather.
Next you are going to need two sticks about the height of your waist with a 'v' in the top of both. You are also going to need a top bar, this needs to be slightly longer than the distance between the two trees. All three of these items need to be strong as its whats going to hold the whole roof up.
Place a 'y' stick next to each tree at a 45* angle and place the top bar across the space, leaning the top bar against the trees so that it stays stood up.
Now you are going to need to collect lots of sticks, these will form the foundations of your roof. The roof will hold together better if you collect sticks with lots of thin branches. These sticks need to overhang when placed at the same angle as the 'y' sticks. When you've covered the whole of one side of your shelter, (don't forget it needs to be the side the wind/weather comes from), you can move on to the next stage.
This is the stage not to be skimped on if you want to stay dry! The whole of the roof is going to need waterproofing. The best materials for this are bracken, and leafy plants. I think bracken works best. Start at the bottom of your shelter and work upwards like you would laying slates on a roof. Ideally this layer wants to be about 10 cm thick.
Stand back and admire what a couple of hours hard work has produced.
If you're planning on sleeping in it maybe add some springy floor material to make it slightly more comfortable. Enjoy! Fires should be made to sit just outside the entrance, remember the whole shelter is made of wood so be careful.
If your short on time and don't plan on spending any time in it, just make one that a child would be able to fit in. On the other hand if you plan on spending longer in it consider some modifications, maybe more of a roof over the front, or re-enforcing the bracken roof with some branches over the top to stop it from blowing away.
In bushcraft we have a policy of leave no trace. This means that when you've finished at the site you should leave things as you found them, demolishing all shelters, making sure all fires are out and any rubbish you brought in is removed.