Here are some useful tools for YouTD
WC3Proxy is an open source tool (repo here) which essentially emulates a LAN environment between players across the internet.
WC3Proxy is NOT a battle.net replacement! You MUST know the IP address of the person hosting the game you want to join
To use, the game host must have ports 6112-6119 TCP forwarded. We also recommend disabling Windows Firewall, since it usually hates fun and isn't really that useful, frankly. Everyone EXCEPT the host should run WC3Proxy.exe and put in the host's external IP address as the server address, and set the game version appropriately. If the host has a game up, it should appear first in WC3Proxy, and also in the LAN game browser of Warcraft 3.
YouTD Helper helps manage your savecode, and runs commands automatically (zoom, auto-oil, etc)
We recommend playing from 0 XP, but if you need it, here's a save code generator you can use. Saves are tied to your in game name, so make sure they match.