What is the best way to organize my active directory structure

What is the best way to organize my active directory structure

i would like to adopt the best structure for my active directory domain,
in order to be able to apply GPO efficiently. Here is my schema :
CompanyName\ServiceName{Users, Groups, Workstations, Laptops}
My first question is about geographical sites : we have two geographical
sites, is it better to create this sort of hierarchy :
CompanyName\GeographicalSiteName\ServiceName{Users, Groups, Workstations,
Laptops} or handling geographical sites GPO using Sites policy ? Indeed,
this organization can lead to have to duplicate some services, if they are
split on 2 sites.
My second question is about the {Users, Groups, Workstations, Laptops}, do
you think there is better organization ?
Thanks very much