After some practice I figured out the simple piece that was missing. You should not try to throw the cards but spin them!
Step 1: Getting started.
Any cards will do, I used cheap crappy paper ones and expensive plastic coated ones and didn't notice a lot of difference.
The main things to keep in mind are:
*Don't try to throw the card! This sounds silly but this is exactly the mistake I was making. The card has no weight and if you try and throw it like you would a heavier object it will flutter for a bit and land about 2ft away. You need to spin the card and this action all comes from the wrist. The faster you can spin the card the better it will fly!
*You will have to put some forward motion into your forearm but this should be a gentle, relaxed motion just to give the card some forward momentum.
*You need to keep your wrist and arm very relaxed. The whole motion does not require a lot of force and you will probably find that the harder you try and throw the card the less likely you are to succeed.
The next page shows the two ways I held the card.