Well, yeah that's the question.
Well, there's the rub. You pay attention to where the cards go into the stack pre-shuffle. Then, using your trained eyes, assisted by your previous study of this and other shuffles, you follow those cards through the non-random shuffle.
Your money will be well spent purchasing Arnold Snyder's "Shuffle Tracking Cookbook", available online at the Gambler's Book Club. It's $50, but it's an enjoyable and informative read.