Don't install a key logger on your computer?
Write down the password and hide it in a different physical location than the wallet.
Make a few wallet backups and store those in different physical locations.
I prefer offline wallets myself.
That sounds like too much effort
What I did was to encrypt the wallet with an impossible to crack randomly generated password (example: r'WRVJ?G2/=Z/,f\ijAGZ#q$&0GvNB), then put it in a password protected RAR archive using another impossible to crack password and then put it on an external HDD that is connected to my PC (Online). That sounds secure enough, right?
But I strip 1 layer of security, because I keep my wallet on my PC (it is still encrypted).
My IT knowledge is above average, so I don't open random files regardless of their origin and treat everything that looks suspicious with extreme care.
I believe the only way of someone stealing my coins is to infect my PC with a very smart trojan that can record me entering the password (which I don't plan on doing as I don't intend on spending the coins anytime soon) and stealing the wallet.dat file.