ok my advice is check out the trick sight by dee christopher, this is a great version of this trick, the best bit is there is no memory work at all.
u show a card to the spectators that has a list of 10 different horror movies on it on the other side there is the memorable sentance structured so that the special letters are all on there.
obviously in the instructions dee goes into great detail as to how to perform it
i dotn know enough about these kinds of tricks to give any real idvice myself, i really dont like them for the simple fact that if they pick that last word u have to go thru all the letters that are wrong before finally gettin to the word to me its not a very good type of trick