Where do you find your private keys in bitcoin core wallet?
Read in another thread i should back them up beyond wallet.dat, so what i should write them down or something? anyway where are they and do you get a new private key for each new address i assume?
You assume correctly...
You need to use the help > debug interface > console (sorry, i translated this, my wallet is in my local language)
In the console, you can export your private keys, but be carefull not to expose them!
How do you mean expose? just as in someone physically seeing them?
Any other mistakes that can be made or is this a simple process?
Indeed, physically seeing them, or malware stealing them... But personally, i would follow shorena's advice... I blindly pointed you to the console, without questioning why you would want to export a list of private keys...
The biggest mistake would be to expose your keys in any way OR not using a HD wallet, and forgetting to export the keys for any new addresses that get generated in the future...
All in all, read shorena's advice, it's more helpfull than mine