Step 4: Re-shuffle
Now repeat step 3, making sure you keep the chosen card ontop of all shuffled stacks, trying to be quick about shuffling, and remaining as descrete as possible about your dirty little shuffling technique. Once your finishing the shuffling process, sometimes I find it good to mock your shuffling and suggest inconspicuously, and slightly cynical that you are lucky shuffling isn't a crucual part in this trick. Make sure its after you shuffle, or that might get them to look closer at how exactly you are shuffling the cards.
One final tip about the shuffling technique:
Try and switch hands with the stack that has the card ontop of it, just so it doesn't look like one side of the shuffle is always landing ontop of the other.