I’ll level with you: In recent years my friendships have been based on a complex calculation that is deciding only two things- how likely the person is to survive an apocalypse and how useful they’ll be in the aftermath. And if that sounds harsh and cold-hearted to you, you just aren’t invested enough in your survival to make this work.
My close group of friends is made up of arty types, who at first glance you wouldn’t think have anything to offer- but you’d be wrong. They’re biologists, fitness enthusiasts, martial artists and weapons collectors. They can make armour and have taught themselves to fight and at least one is borderline psychopathic. These are the people I want on my team. And they want me on theirs. We share loyalty and concern for each other, making us a tight and intelligent team right from the outset. Not only could we survive, but we could rebuild- and rebuild a civilisation, albeit one ruled by a benevolent tyrant (me).
Could your friends promise the same? Be honest with yourself. Your best friend- I’m sure they’re great, but could you trust them to stand back-to-back with you as the zombies circle? Would they actually be any good?
Find out their skills. Encourage them in the ones that are most useful after the end- it makes sense for your survival and it makes you look like a good friend. As for the ones with no useable skills- well. You’re going to have to make a tough decision. Would you rather cut the useless dead weight out of your life now, or would you rather shoot them in the head while they’re being torn apart by zombies/mutants/badgers/nameless horrors? It’s less painful to drop them now. And if it makes you a pathetic, lonely shut-in, well, what price survival?
Still, don’t throw them out on their arse too soon. Even the most useless seeming skill (basket-weaving, ballroom dancing) could have a use in the rebuilding stage. As long as you think they could be kept safe until that stage, why not keep them along for the ride? But be honest. Are you sure you want to make that level of effort for them? After all, they have a really annoying laugh.