I think the biggest mistake a lost person who really needs a shelter makes is that they wait too long before they decide to make a shelter. Most people who die in the wilderness do so from exposure.
A lost person thinks they are going to find salvation just around the next bend, or just over the next rise. The problem is that this thinking keeps on until they notice darkness is falling and it is almost too late to put any kind of effective shelter together.
Location, Location, Location
The next problem is many people pick the wrong location for their shelter. By just looking ravines makes a nice location for a shelter, but are prone to flash flooding. Avoid them because they can be deadly. Many will fail to look overhead when building their shelter, and end up with a dead tree, or large rock that could come down on them in the middle of the night.
Where I live unless the forest has been logged you can’t completely get away from large trees that may come down or drop a big branch on you. The best bet here is to find a large downed tree and build your shelter against it. This way the tree will take the blow, and hopefully spare you if something does fall.
Wind Direction
One of the most annoying things is to get a nice shelter built and then put in your fire, only to have the smoke inundate your shelter because you didn’t take the wind into account when you built it. A good angle away from the wind is best.
If you place it directly away from the wind the lee will cause the smoke to eddy and back up into your shelter.
Fire Safety
So you have a nice shelter built and warm fire in front only to be awakened from a deep sleep by your shelter being on fire! Basic fire safety is important especially in a survival situation, where what would be an inconvenience in a normal situation, can be fatal if you are lost. There should be some thought put into building your shelter other than just the mechanics of building it

Dennis Diaz is the Chief Editor of Survival Ready. He is an avid survivalist who is passionate bout learning and teaching survival and preparedness skills and strategies. Author of the The 12 Month Prepper & Survivalist Playbook.
He enjoys helping others prepare themselves for multiple dangerous scenarios, by coaching them on how develop their own customized survival & preparedness plans and develop their survival skills. He teaches his students and readers to make preparedness and survival knowledge part of their daily lives.