I think the first major piece of planning would go into deciding what type of model you are going to use, Domain or Workgroup. One major factor that you should take into consideration is security. If security is what you are going for then go withthe Domain model. If security is not a big factor and ease of setup is, then go with Workgroup. Next would be coming up with what protocols you will need for the network. TCP/IP would be the first obviuos selection, and maybe Netbeui if the network does not need to be routed. These are, to me anyways, the first logical steps in preparing a network. Next would probably be the roles you want your PC's to play on the network. The only real planning involved with this would be if you elected to go with a domain model, in which case you would have a server (domain controller) and clients connecting to the server. In a workgroup environment this would not matter as all PC's are equal (meaning all PC's are potentially servers and clients nomatter what the OS they may be running). A domain model would be a little more time-consuming to setup, but less administration on your part. As where a workgroup model would be easier to setup, but more administration on your part. You gotta give a little to take a little. I hope that this can at least get you started or pointed in the right direction. If you supply some more specifics as to where you are setting this up and what you would like the end result to be, I'm sure you will get alot more specific info. You can email me if you wish.
Good Luck.
Norm