The most difficult part was filling out some tax information. If you're not American you will need to be able to prove it too.
If you have a logo / main image in mind for your game you'll need to provide a lot of different dimensions for it. Knowing how to use Gimp (or photoshop) might be the best skill to have for this part.
You'll need to take a video recording of your game too. I suggest Camtasia Studio.
You will need to pay 100 USD before you can do anything.