From an online article:
Start with an original but memorable phrase. For this exercise, let's use these two sentences: "I like to eat bagels at the airport" and "My first Cadillac was a real lemon so I bought a Toyota". The phrase can have something to do with your life or it can be a random collection of words—just make sure it's something you can remember. That's the key: Because a mnemonic is easy to remember, you don't have to write it down anywhere. (If you can't remember it without writing it down, it's not a good mnemonic.) This reduces the chance that someone will guess it if he gets into your computer or your e-mail. What's more, a relatively simple mnemonic can be turned into a fanatically difficult password.
Which brings us to Step 2: Turn your phrase into an acronym. Be sure to use some numbers and symbols and capital letters, too. "I like to eat bagels at the airport" becomes Ilteb@ta, and "My first Cadillac was a real lemon so I bought a Toyota" is M1stCwarlsIbaT.
That's it—you're done. These mnemonic passwords are hard to forget, but they contain no guessable English words. You can even create pass phrases for specific sites that are coded with a hint about their purpose. A sentence like "It's 20 degrees in February, so I use " lets you set a new password every month and still never forget it: i90diSsIuG for September, i30diMsIuG for March, etc. (These aren't realistic temperatures; they're the month-number multiplied by 10.)

