Randomly generate passwords of 20+ characters using your password manager. Alternatively, use the built-in passphrase generator, and store these passwords using your password manager.
If you want to memorise a password, then I recommend generating a random passphrase containing 6+ words.
If you want to send someone an encrypted file, then I recommend encrypting the file using your private key and their public key. When decrypting the file, if you know that the sender's public key belongs to the sender, then you can be sure that the encrypted file was sent from them.
Alternatively, you can encrypt files with a password and share that password using an end-to-end encrypted messaging app like Signal or Element. This is easier for sharing files with multiple recipients. However, be sure to regularly change passwords.
Only ever share your public key. You can send someone your public key as a string or as a
.public file. You can safely share your public key via an insecure channel (e.g. via a messaging app).
Always back up your
.private key files to external storage. You can recover your public key from the private key, but if you lose your private key, you will be forced to generate a new key pair.
If you believe your private key may have been compromised (e.g. you accidentally shared it), then you should decrypt any files encrypted using that private key and generate a new key pair. You can then use the new private key to re-encrypt your files.
I recommend randomly generating keyfiles using Kryptor. Randomly generated keyfiles are made read-only and unlikely to be accidentally modified since you have no reason to open these types of files.
However, any type of file (e.g. jpg, mp3, zip) can be used as a keyfile but using an ordinary file type is riskier since it is more likely to be accidentally modified.
Always back up your keyfiles in case they are accidentally modified. I recommend keeping your keyfiles offline on memory sticks or external hard drives.