A Debris Hut
OK, the worst has happened. You're forced by circumstances to leave the relatively cozy environs of your home and supplies and must bug out to a new location. Let's imagine further that somehow you've lost your tent, or had it stolen. There are ways of coping, but the best one for making shelter in just about most climates in the US is the debris hut.
There are many websites and books which describe the best way to make one. The first one I ever read was way back when, eons ago, the first Tom Brown book on Surviving in the Wilderness. The video listed above is just about the best one I've seen. It's highly practical knowledge, and can be taught to children as young as seven, and easily constructed.
It takes time, as the video details. It's not like the rapid popup tents we have now, but then, it will keep you extremely warm due to the insulated structure, and of course is ideal since it's camouflaged.
I won't go into specifics since the video is so excellent. The main thing is NOT to make it too big. Make it precisely big enough for no more than two people (one is better, but then sleeping with your honey is worth a little extra work). You can easily make a ring of these and have a very cozy spot for a couple of days. They hold up well, and can last far longer, but if that's what you have to do, it's far better to make a mud and wood structure rather than a debris hut.
If the very worst happened, and you had to travel the back roads to get to your destination, you could easily construct one or more of these, and then after resting, continue on your journey. Based upon the depth of the upper insulation you put upon it, the structure can be pretty waterproof.
I highly recommend this as a family project to be attempted while actually camping or hiking. The kids will love you for helping them make a "fort" and will have the most fond memories of making one.
If the weather is clear and warm, it's overkill to make one. Realize though that a forest can get quite chilly at night due to dense shade. There can be dramatic temperature variations when camping, something a greenhorn is always surprised by.
If security is an issue, and it is not possible to build a fire, having a warm burrow to sleep in will greatly assist you in drifting off to sleep.
Mike goes into the construction over several videos which can all be seen on youtube.