This is how i keep my private keys safe since i can't afford to buy a hardware wallet.
1. A complete new harddisk
I bought a new harddisk and install window 7 on it and copy all my private keys in there, i don't bother to leave this harddisk in the pc, after the copy is completed i remove the harddisk and keep it.
2.My Recording book
I have a long hard shelled book that i use for keeping records of all the airdrops and bounties i promoted because sometimes i used to forget easily so i write down my recovery seeds in this book as well
3. Flash Drive
I have a good 8gig flash drive as well that i use to copy software and files from one pc to another so i format this flash drive and copy my private keys and recovery seeds in it.
At first no one knew i am into crypto stuffs and secondly i don't share my room with anyone cos i am living alone, those who have people around them with face problems like friends going behind your back checking through your stuffs or even stealing your things, hardware wallet is still the best though.
On 1 be sure that it is really well hidden a vault will do provided you have a big amount of coins that have a good potential in the market
On number 2 That's ok if you don't have a little brother or sister who will not mess up with those books
On number 3 be sure to make it really hidden people might be curious about what on it it's probably not the safest of the three because everyone can readily see what's on it.