Tree-Pit Snow Shelter
If you are in a cold, snow-covered area where evergreen trees grow and you have a digging tool, you can make a tree-pit shelter.
To make this shelter–
Find a tree with bushy branches that provides overhead cover.

For warmth and ease of construction, this shelter is one of the best. When shelter is essential to survival, build this shelter.
To make a debris hut –
Build it by making a tripod with two short stakes and a long ridgepole or by placing one end of a long ridgepole on top of a sturdy base. […]

In a marsh or swamp, or any area with standing water or continually wet ground, the swamp bed keeps you out of the water. When selecting such a site, consider the weather, wind, tides, and available materials.
To make a swamp bed–

If you are in a wooded area and have enough natural materials, you can make a field-expedient lean-to without the aid of tools or with only a knife. It takes longer to make this type of shelter than it does to make other types, but it will protect you from the elements.
You will need two […]

A one-man shelter you can easily make using a tarp requires a tree and three poles. One pole should be about 4.5 meters long and the other two about 3 meters long.
To make this shelter –
Secure the 4.5-meter pole to the tree at about waist height.