StoSoutdoors

  You must also remember the problems that could arise in your environment.
Avoid flash flood areas in foothills.
Avoid avalanche or rockslide areas in mountainous terrain.
Avoid sites near bodies of water that are below the high water mark.
In some areas, the season of the year has a strong bearing on the site
you select. Ideal sites for a shelter differ in winter and summer. During
cold winter months you will want a site that will protect you from the
cold and wind, but will have a source of fuel and water. During summer
months in the same area you will want a source of water, but you will
want the site to be almost insect free.
A shelter can protect you from the sun, insects, wind, rain, snow, hot or cold temperatures, and enemy observation. It can give you a feeling of well-being. It can help you maintain your will to survive. In some areas, your need for shelter may take precedence over your need for food and possibly even your need for water.
  Assess the situation. How long do you think you will need your lean-to? How urgently do you need to make a lean-to? Theses things will let you know how strong to make your shelter, or how much time you need to spend on it.
Scan the ground, find some sticks, about the size of two thumbs width. If you can't find the right size, make due with what you can find. If you have a pocket knife on hand, cut them off of short trees, preferably without leaves, branches are fine. You will need long limbs.
Look around you. Find a few large trees, if you can find a particularly large one, that’s very good, if not, find a few that are very close together, perhaps a foot apart. Check the warning at the bottom of the page.
Start to lean the sticks against your tree. Make sure that you leave space between the end of the stick and the tree for your body to comfortably rest, make sure the sticks are going to stay and not blow away, this is why you should use thick sticks. Leave a little bit of space between each stick. If your sticks are small, lap them over each other and ignore the last sentence.
Get some leaves together and stuff them in the little spaces in your lean-to, this will insulate you some from the cold, and cut back on wind chill. Pile the leaves on, for a better effect ,and if you have the time, put more sticks over the leaves.
Stuff more leaves in your sleeping space, if you want, you can lean more sticks at one end of the enclosure to feel more snug.
Crawl in and sleep, or rest. You must be tired from making your lean-to.
it is important to know how to make a temporary shelter for you to spend the night in. I have had to make a lean-to on many occasions due to my interest in forest and wildlife. Follow my steps, and maybe next time you have to ‘burrow in’ for the night, you will find yourself more comfortable than sleeping in the bare wind and elements.
Pile all manner of debris - moss, leaves, pine needles, dried fern or whatever nature makes available - on top of your structure.

  Tie off the hood of the poncho. Pull the drawstring tight, roll the hood long ways, fold it into thirds, and tie it off with the drawstring.
Cut the rope in half. On one long side of the poncho, tie half of the rope to the corner grommet. Tie the other half to the other corner grommet.
Attach a drip stick (about a 10-centimeter stick) to each rope about 2.5 centimeters from the grommet. These drip sticks will keep rainwater from running down the ropes into the lean-to. Tying strings (about 10 centimeters long) to each grommet along the poncho's top edge will allow the water to run to and down the line without dripping into the shelter.
Tie the ropes about waist high on the trees (uprights). Use a round turn and two half hitches with a quick-release knot.
  Spread the poncho and anchor it to the ground, putting sharpened sticks through the grommets and into the ground.
If you plan to use the lean-to for more than one night, or you expect rain, make a center support for the lean-to. Make this support with a line. Attach one end of the line to the poncho hood and the other end to an overhanging branch. Make sure there is no slack in the line.
Another method is to place a stick upright under the center of the lean-to. This method, however, will restrict your space and movements in the shelter.