How to find an IP, Mac Address, and Service Tag using Command

Open command prompt (start menu > cmd or C:/windows/system32/cmd.exe)

The following command will display the service tag of the PC you're on.
bios get serialnumber

If your looking for the tag of a different PC on the same network type the below command instead.
wmic /node: 10.11.12.123 /user:username /password:password bios get serialnumber

where 10.11.12.123 is the IP of the PC and user/password are admin account credentials.

To find the IP of a computer on network type the below command.
nslookup pc-name

To find the MAC address of a computer on network type the below command.
arp -a 10.11.12.123

where 10.11.12.123 is the IP of the PC.