Basically, you have a certain amount of skill points to use on each one. With 4 being the best you can get on each one. You have to pick which you prefer out of Attack and Defense though.
I think that's pretty good sim you've got there. Interesting about home and away grounds advantage - do you reckon if they're in the same country it might be less so or is this just a pointless point to make (damn that sounded weird )?