HOW TO CHOOSE FREESTYLE WHEELS ?
Most important thing to turn any board into a freestyle board: WHEELS.
In freestyle we use OFFSET wheels. This means the bearings are on one side of the wheel whereas street regular wheels have the bearings centered.
Freestyle wheels cover the axle and help a lot for stability in rail, and makes some tricks possible such as coconut wheelies, rail toespins, railwhips...
You now have to choose the right durometer depending of where you skate, what do you want to do and your personnal preference.
Softer wheels (93A-95A) are good when you skate rough surfaces or very slippery surfaces such as Bordeaux's infamous marble or IndustrieMuseum's floor (LOL)
Medium hardness (96A-98A) is good for all terrains, its a good medium point to get started with.
Hard wheels (99A +) is good for fast rolling tricks, loooooong coco wheelies, or if you're a fast japanese wizard... Hard wheels are for you.
Here are some links where you can find the best freestyle wheels: