Welcome to the wonderfully addicting world of throwing sharp implements!
You've already been given good advice and I can't can't improve on it, so I'll just try add to it a little.
Rather than moving the playing card around on your 'hawk block (once you get all your pumpkins "carved"), just staple about 4-5 separate cards on different areas of your stump. Then you can still choose a specific target and have the option of throwing at a different target each time if you'd like - Once you start getting reasonably proficient, you can even have a bystander call out which target to throw at on a given toss. (That'll really be a good test of how adaptable you can be.)
I'll also, from time to time, [strike]steal[/strike] borrow some yarn from Mrs. Kansan and criss cross the block in varying patterns with the object being to cut a specific strand on a given throw. Of course I realize that all this is going to be a ways into the future for you, but at least you've got some ideas to make it more fun and challenging.
Once you get pretty good at a single revolution throw, you can start working on 1 1/2 revs ('hawk head pointed backwards, throw from about 9 - 9 1/2 steps) 2 1/2 and double and triple revs, depending upon how much room/how good a backstop you've got.
I also practice (and demonstrate) from pretty much every position I can think of, i.,e., standing, kneeling, sitting down, lying down, etc... and use a variety of tossing methods from simple overhand to sidearm and underhand. You can also try throwing with your off arm. It's all designed to make me more proficient and increase the fun factor. When demonstrating for groups, I'll sometimes have an assistant toss (one at a time, usually) 'hawks and throwing knives to me so that I can throw up to 8 or 9 times (I've got 6 'hawks and 3-4 throwing knives) in a row just for the wow factor for the audience. :haha:
Again, welcome to the club! As someone mentioned earlier, start off easy. Don't throw for more than 10 - 15 minutes at a time and don't let the frustration get to you if you don't stick every single time. I've been tossing 'hawks for 30 + years and still have an occasional crappy day. Also, make sure you have some spare handles because chances are you're gonna' break a few! Don't sweat it, it's just part of the game.
One last thing - I, personally, never let myself quit on a bad throw. If I'm having an off day and can't cut the darn string or get a hawk to stick and I'm gettin' flustered :cursing: I take a deep breath, close my eyes and visualize the target... Then I open my eyes, rare back and walk up and chop the sunuvab*tch! :thumbsup:
Luck to you! :hatsoff:
...Kansan...