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.
Step 2: How to hold the card.
The first way was to hold it in-between your index and middle finger at a slight diagonal with the tips of your figures on the corner of the card. When you throw it you want the card to pivot around the tips of your figures to give it a spinning motion.
The second way is actually very close to the way I hold cards when I'm dealing. Hold the card in the middle with your thumb and middle finger and have the tip of your index finger on the corner of the card. As you throw it you use your index finger to add the spin.
Step 3: Throwing technique.
Remember! Do this gently, trust me it will work much better this way then trying to put lots of weight behind it.
Once you get the technique down (which if I have explained this properly should be on about the 2nd or 3rd card you throw) you can get good distance on every single card.
The more you practice the faster you will be able to spin the cards and the further and faster you will be able to get them to fly.