Creating network diagrams is an art itself. While I’ve never found a ‘general guideline’ on how one should create these diagrams, experience shows that following major vendor trends often brings you close to the methodology you need to adopt.
For example, Cisco diagrams are considered to be extremely well made and designed. They don’t contain too much information regarding the design, thus avoiding ‘cluttering’ the diagram, but also give the necessary information to help the engineer understand the necessary information. Adopting similar design schemes and adding the information you believe is required, will surely provide a great result.
One of the most popular programs used to create these type of diagrams is Microsoft’s Visio. Cisco and other vendors offer free of charge visio icons that you can download and use for your diagrams.
Following is a link from where you can download Cisco’s offerings for Microsoft’s Visio:
Hope that helps,
Previous Member’s Answer: ( Labnuke99)
A good start would be the SearchNetworking article on the OSI model. The next place to research would be the online TCP/IP guide article on the OSI model.