Hello Michele31415,
As I don't have 1 yet, best advice is that Common Ground is ALWAYS the biggest trace that goes all over and around on the board the 5 and 12 volt pins are likely short and only go to devices for a short distance and tend to jump around, they are in naturally very skinny. Typically at every chip there is a "trash" filter at the head of each chips power in, a .01 uf cap is used mostly for this.
Chris
