To make a blockchain.info wallet as secure as possible:

Use two factor authentication.
Use a complex password.
Keep an encrypted backup copy of your wallet somewhere secure (USB in a safe?)
Use the browser extension.
Don't access your wallet from a publicly shared computer.
Don't install any pirated software on your computer.
Be extremely selective about what software you do install/run on your computer.
Don't access any other websites while accessing blockchain.info

If you are looking for something "bullet-proof", then you need to consider either Armory or paper wallets.