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.)