Where Are They?
Your next task is to draw your devices in relative position to each other. Don't worry, you don't need any fancy technical drawing skills for this – just drawing general proximities. If you want to get a little more complicated, you can draw which devices are in which room and against which wall, but that will only really come in handy if you want get into the nitty gritty of the best placement of, say, your wireless router. Your home network diagram can be as abstract or as concrete as you want it - though the more sticks to reality, the more useful it will probably be for planning purposes.
Of course, many devices are mobile and are used throughout the house, be they laptops or Bluetooth enabled cellphones, so placing them may seema little difficult. Tentatively place them where they are most commonly used, for instance a laptop on the dining room table or on the living room coffee table. If there are multiple such favorite places, dotted outlines are an easy way to represents them.
Don't forget to show where LAN and other ports are, either, even if you're not using them. If you aren't intimately familiar with the walls of your home, get to know them: previously unknown broadband ports can be a happy, unexpected boon.
If you're dealing with a house with multiple stories, then using multiple pages for your diagram is probably a good idea for the sake of coherency.
If the diagram looks like it's going to be really complicated, a little color coding can go a long way—nothing fancy, just make sure to make a well-labeled key on the corner of your paper for each device.