There are many ways of generating secure brain wallets. One would be by employing the use of a "live" and offline operating system using a reputable wallet, such as electrum. Once your wallet is generated, you can write down all of your public addresses, and memorize your seed, (you should develop a way to get at your seed in case you forget it) and then take the wallet offline where it can remain in cold storage for a very long time. This method would likely be very safe. The amount of security you should employ depends on the amount of funds that you are trying to protect. People will be willing to work a lot harder to get at something that is worth a lot to them. Keep in mind that the physical security of the device (e.g. computer, tablet, phone, hardware wallet, etc...) is very important.
this thread isn't really to warn you any longer. you're dead set on using brain wallets no matter how many others try to warn you off the idea.
brain wallets are not a safe way of storing your bitcoins. but no one's stopping you doing that.
but if you want best practices for keeping bitcoins safe then brain wallets, aren't it! 'nuff said. Its a warning to others, as you, marbu have your mind set on doing it.
its your life, marbu. i really hope that it works better for you than it did for me.