What is the most secure way to generate a private key for a user?
Is this secure?
Hashing a password that the user inputs (longer than 10 characters with numbers, capital letters), then hashing with the current date and time, then hashing with random number generated between 1-100,000?
Does anyone know how is private key generation handled in other clients?
I think that you best take a look what the code of
https://www.bitaddress.org does, since it is available on GiHub.
Since that code is proven by time that's good, the security is mostly related to the internet.
So one pretty safe way is to download the bitaddress code locally, onto a stick, for example, unplug the computer from any internet activity (go offline), generate as many paper wallets you want (meaning public+private keys actually), print them to paper (printer connected by USB, not the network).
Afterwards stop the printer, format the HDD and after that you can reinstall and go online again.
Safe enough?