Ajmal took 50 wickets in eight Tests last year and often surprises batsmen with a doosra, a ball that drifts away from a right-handed batsmen.
Ajmal wouldn't reveal his newly developed delivery, but said on Friday, "It's not far, you will know it."
The three-Test series begins in Dubai, United Arab Emirates on January 17, and Ajmal hopes the pitch will suit spinners. He grabbed eight Sri Lanka wickets in a Test at the same venue in October 2010.
The offspinner has not targeted any specific batsmen but has been watching videos of the Englishmen.
He says, "We have special plans and are working on that."