One way to construct a somewhat easily remembered long password is to think of a song, poem or somesuch, which you could remember in your sleep, and then apply some algorithm on the words.
As an example, pick the first three letters of each word from the first line of Paranoid:
Finished with my woman 'cause she couldn't help me with my mind
Then pick some characters to delimit the letters and maybe start or end the password. Make up some rule by which you make some of letters uppercase. For example:
3Fin.wIt.my.Wom.'Ca.she.Cou.hEl.me.Wit.mY.min%
That's 46 characters fairly easily remembered. Half of that would be enough, and in fact 3 letters may be a bit much since I ended up with a couple of dictionary words in there.
(You want the brute-force search space be large: use 1 or more characters from each group: uppercase, lowercase, numbers, symbols.)
Here is a much simpler way to create easy to remember (not only
somewhat easily remembered) and secure passwords: Use a complete sentence as your password! If it has more than four words, it is secure enough, and if you make it a bit obscure, nobody can guess it. So instead of
3Fin.wIt.my.Wom.'Ca.she.Cou.hEl.me.Wit.mY.min%just use
Finished with your wife, although she helped my cat.And BTW, forget about these special characters and such. The blanks that separate the words suffice. Special characters only make your password more complex and harder to remember. If you are concerned about the security, just choose a sentence that is a word longer.
Why? Because nothing beats length! (an increase in length adds to the exponent of the complexity, one more special character only adds to the mantissa).
In other words: Just make words the atoms of your "password" and you win twofold:
1. It easier to recall a (near)-sensible sentence than a single word (or the trace your cat left when it walked over your keyboard).
2. It is much more secure, because it is harder to crack (both by a dictionary attack and by simple brute force).
Here is the downside: It will take you longer to enter your password...