In the Wasteland people are going to want to intimidate you. If Marauders, Scavengers and other opportunists can get you to roll over and bare your soft underbelly, all the better for them.
Predators don't like to waste time, or take damage.
If you're holing up somewhere good, you're going to want to build barriers for vehicles. Predatory types like to use vehicles to get around, and they like to use the noise and size to intimidate. If you can make barriers for ‘em, they're more likely to just mosey on, look for easier pickings. Make it cost them even to just come check you out.
Social interactions can be a killer in the Wasteland.
Keep your barriers as natural as possible, use what you find in the environment. Barriers made of high quality resources or valuable objects are just going to get stolen. What's more, they're going to alert folks to your wealth, or even just the fact that you're there.
The more inconspicuous you make the barrier, the better, the number one thing the predator is concerned with is “Is it worth it”? Most of these types are not going to want to clear a whole bunch of trash out of the way, they don't want to have to lift rocks, cut wood, shovel earth, lift debris for an unknown reward. They just want to roar in there and take tribute from your shaking hands, and whatever else they want.
Ideally what you've made will look like a landslide.
The Wasteland is where we all get animal, we get into our animal natures. You're going to have to trust your instincts, sure they're buried somewhat, but in the eerie silence of the Wasteland you got nothing else to do but get back in touch with 'em.
Course, barriers are not going to stop everyone, just the more opportunistic types. There will be certain Denizens of the Wasteland who will press on through your rough and ready fortifications
but dealing with them is a story for another time.