What NOT to do When Documenting Your Customers Networks

Do:

Use a tool like LucidTrac's Hostname and IP Management tool to keep track of all the devices on your network. This tool allows you to easily add, edit, and delete entries, as well as sort and search by hostname, IP address, or location.

Don't:

Try to keep track of everything in your head. It's just not possible. You'll end up forgetting something (or someone), and then your customer will be angry with you for not being able to fix their problem.

Do:

Keep a list of all the IP addresses assigned to devices on the network, as well as what each device is used for. This will come in handy if you ever need to troubleshoot an issue or make changes to the network configuration.

Don't:

Rely on DHCP server logs to keep track of IP addresses. These logs can be hard to decipher, and they're often not updated in real-time, so you may end up with inaccurate information.

Do:

Use comments and annotations liberally when documenting the network. This will help you (and others) understand what's going on more quickly and easily. 
Annotations are especially important if you think there's a chance someone else might need to take over for you at some point.  That way, they'll have all the information they need to hit the ground running.  
Just be sure to use clear and concise language so that everyone can understand what you're trying to say.       

Don't:

Write a novel about every single device on the network. No one wants (or needs) that much information. Just include the basics like hostname, IP address, operating system, and Function/ purpose within the network   In most cases, that's all you'll need.                                                                                            

If you must include additional information, consider creating separate documentation (perhaps using a wiki or similar collaborative platform) that people can reference if they need more details