This reminds of my coach when I was little. He got really fed up with us skying PK's over the bar and otherwise missing horrendously, so he made us spend an entire half practice just taking PK's.
He told us all to aim right for the keeper's belly and just kick it as hard as we could. We were like "Why kick it right to him?" And he was like "Because you are all terrible and will miss by at least three feet. So pretty much if you aim right for the keeper you will end up putting it right in a random corner somewhere."
We all refused to believe we were that bad, so finally he said "Okay, look. If you nail it right at him, he will miss it because he will most likely dive. And if he does get it by some chance, you'll hit it hard enough that it will just bounce straight back to you and you can put away the rebound."
We thought that was rather clever and bought it. So we followed his instructions accordingly. Turns out he was right the first time and we all missed by like a yard high and two yards left or right and ended up scoring just about every time.
I never missed a PK again.*
*Disclaimer: As a horribly mediocre midfielder, I was never the PK taker. Or even in the first five for shootouts. As I result, I only ever took two PK's. But I did score both times!