You need to take your threat model into account. Will people literally destroy a house to get your backup password? Will anybody even look for it?
You also need to take into account how likely you are to forget the password, and what kind of information will be available to an attacker that recovers it.
Assuming that you are not under a severe threat, simply writing it down and storing it in a fairly secure and nondescript hiding place will do. Place it in a book, tape it underneath your sock drawer, etc.
If there will be people actively looking for it, you may need to take more spycrafty (is that a word?) steps, such as laminating it and burying it in the ground, placing it in the freezer inside a piece of frozen fish, spackling it into a wall and painting over it, placing it inside a pen, etc.
You can also take several random values, xor them together, and use that as a key to encrypt it. Keep the encrypted copy in the open, then store the random keys in different locations, so that all will be required to regenerate the key and unlock the password. This may be a more secure method regardless of how the distributed secrets are hidden, because it will increase the work of someone looking for it, especially if they do not know how many secrets are required to regenerate the key.
If the information is very sensitive, you should increase the security level even if the threat is low. Required security = threat level * damage from exposure, in this case.