|You could use one subnet in all 4 locations. If you have less than 200 clients total.|
Figure out the number of clients per location and ensure that each has a large enough pool of IP's available to support that location.
Site 1 (20 users)
DHCP Scope: 192.168.0.50 through .75
Site 2 (30 users)
DHCP Scope: 192.168.0.100 through .140
Site 3 (10 users)
DHCP Scope: 192.168.0.150 through .165
Site 4 (35 users)
DHCP Scope: 192.168.0.170 through .210
This allows you to traverse all locations, avoid overlap of the scopes (and therefore duplicate IP issues) and gives everybody at each location internet access.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.