The usual method for BTC-cold-storage is well known (Generate key-pairs with the bitaddress-page on an offline computer and so on. Details here for exampe...)

Problem: Paper Wallets have to be printed out. And to be secure you should store them at different places. And there goes the security... Maybe someone manages to take a photo of the address-pairs and you're f***ed.
Brain Wallets can fix this, but you have to choose very long passphrases. And if you are not recalling your passphrase from time to time, you will forget it (Don't overestimate your powers...).

Solution: So I'd like to suggest a method that fixes both of the aforementioned problems:

Pick sentences from your favourite childrens book or from your favourite poems, lets say:

Quoth the raven, “Nevermore.”
Bob the builder: Can we fix it? Yes we can
... and so forth.

The above (incomplete) method yields the passphrase

ravennevermorebuilderfixwe

You now can write on a piece of paper as your memorizing-aid:
Quoth the -, “-.”
Bob the -: Can we - it? Yes - can

To apply this method correctly, you obviously shouldnt choose phrases like those above as they are too easy. Anyone knows them. But when I flip the pages of my favourite children books (or poems, or things my mom said to me that stuck or....) I always stumble upon everyday-sentences, that have no importance to anyone but me: For me they were (for whatever reason) highly memorable. You can write down the sentences, by replacing the relevant passphrase-words with a dash. Ideally not even your close family members are capable of filling these dashes with the right words. So you can write down these clozes, which is for you like a perfect reminder, but useless for anyone else.

Advantages: You can produce very lengthy passphrases you do not need to memorize, as you can write them down without giving too many hints to others (ideally)

Disadvantages: Close to random choice of words, but not perfectly random.

Question: How many words do you think you have to collect with this method to meet standard-brain-wallet-security?