If you want to be able to write things down without making a mistake then it is very difficult to do with with a WIF private key that is a long random alphanumerical characters. It is a lot easier to write down words, which you can do if you use a deterministic wallet like Electrum that generates a mnemonic (12 words) that are easier to write down. That way you have the benefit of also being able to generate more than one address from those words which comes in handy in the future when you want to spend your coins (avoids address reuse).