How do I secure my house for the apocalypse?
Your best bet, and not necessarily your most expensive, is installing high-end steel doors at entry points, with steel frames and heavy-duty locks (remember to get secure bolt-style locks for the bottom of the door, too). A big plus is that steel doors generally run cheaper than wooden doors.
How do I fortify my house?
Fortifying Your Home: Things to Consider. Most people have already considered moderately-effective security improvements such as getting an alarm system, installing deadbolt locks on exterior doors, installing exterior lighting all around your home, trimming trees and shrubs around windows, and getting a dog.