Network Diagram

aha! you see the value of this already!
you are going to have big wheel with main switch at center spokes to other devices or subwheels with cascaded switch/hub at subwheel centers. if not easy to determine which computers are physically connected to cascaded switch/hub, just leave hanging in air not hooked up for now. because that is nice to know but not that important for effort required imho i say just get the hardware down and don't 'hook it up' identify everything about it that you might want to know later like if you needed to re-set things up. leave stuff blank if unknown, you can pencil in later as you find out.
eg: role of computer (workstation, domain controller, dns server, dhcp server browse master etc etc) mac address, network name, dhcp or static (ip address if static, dhcp servername if dhcp client) on the public devices (probably your router) you will have an 'outside WAN' and 'inside LAN' ip address, subnet mask, gateway address, dns servers(s) domain name (lots of stuff might be same for all so don't have to include on each, just make Note: on diagram.
that will give you the 'picture'.

Would suggest;

1. Page 1 contains major components (with connections/ports/IP if assigned)/circuit connections (with circuit ID's you would use to report outage)/functional areas off each hub/switch

2. Additional pages would be for the functional areas (ie: admin, maintenance, stockroom, etc,,,) showing connections w/ports connected to and overview of where it comes from.
You can actually draw out the equipment, then copy and paste duplicate equipment to other pages.

3. To discover netowrk routing, go to first router after the server and internet/isp access circuit. From a DOS window tracert to each server/equipments IP, this will show how they get to the server/internet (ie: routers/switches they go through to access the server/ISP). Or last resort trace the cables, very time consuming !

BTW - Hardest part is if you are using Frame Relay on a WAN, need to show DLCI's on the individual PVC's. Frame Relay is a cloud, no fixed route between the 2 access circuits only fixed termination points.