Find a breathing mask immediately. There are things in the air — small, microscopic things, that float like pollen and enter through your nose and mouth. If you’ve ever been out and thought you smelled something sweet, like cotton candy, it’s too late. Your lungs are about to liquefy, slowly, cell by cell. Sorry about that.
Only drink from fast moving streams. It doesn’t matter if you’ve got a water filtration unit — never collect water from ponds or lakes. It’s not because of the dead bodies. It’s the half-dead ones. They can stay down there for months at a time, just waiting for someone who doesn’t know better.
Stay away from settlements. Any half-decent settlement already has too many mouths to feed. If you ask, they’ll let you in. But they won’t let you stay. They’ve got all those hungry mouths after all.
Don’t eat the birds. I don’t know what these new birds are, but they smell like tar and their meat can burn a hole in your throat. Stick with canned goods and cockroaches.
It’s safe to travel by night. But if you hear a sound like a ticking stopwatch, stand perfectly still and wait until the sun comes up. They’ll pass you by as long as you don’t move.
Don’t aim for the heart OR the brain. Aim for the legs if they can walk. Aim for the arms if they can crawl. Don’t assume anything will stay down for good. Just make sure you can run faster than they can.
Red sores heal with time. White sores will rot down to the bone within 48 hours. Remove the limb. Cauterize the wound. That should buy you a few weeks at least.
The living don’t knock. If you’re holed up somewhere with four walls and hear someone knocking, ignore it. Whatever it is needs you to let it in and you really don’t want to do that.
Don’t be alarmed if you see angels. It’s normal to see beings made of soft light descending from the heavens. It just means there are parasites attached to your optic nerves. They can’t kill you. They’ll just consume your eyeballs from the inside out.
Always leave one bullet for yourself. It’s a brave, difficult thing to make a life here in the After. But eventually you’ll get tired. Eventually you’ll see that of all the things you can do during the apocalypse, surviving might just be the worst. But that’s for you to discover. Until then, good luck.
And for fun, here's the same story, read and illustrated (in a manner) by a YouTube channel called Tales of Tim: