If you live in an urban or suburban area, it will be next to impossible. You’ll need multiple sentries to stand watch 24/7. Either work out a plan with your neighbors for mutual sentry and food- and water-gathering tasks or have a remote retreat location.
Frankly, if we get to this point, there is very little chance that you and your neighbors, even if heavily armed and trained, will be victorious against the masses from from the urban and suburban areas that go out seeking food.
You really need to have a remote location, preferably in a small farming-type town of like-minded people.
As the experts say, why wait? Getting out of dodge may be a problem in itself. Move there now and be all set up for WTSHTF.
I partly agree. Ayn Rand saw the inevitable and incorporated the eventual solution into her novel; distance and concealment as the only defense against anarchist thugs.
But, when you’re tied to the city for your livelihood, it’s kind of hard to live too far out. I moved as far out of my large metropolitan area as was feasible, and am semi-rural, but still too close (2 miles from an interstate loop.) Nice idea, but not practical, unless you are independently wealthy already.