These topics have been pasted a little too much.
With all seriousness, the most useful place to find 20,000 different answers are:
------------- eAthena -------------
http://www.eathena.ws (http://www.eathena.ws)
http://www.eathena.ws/wiki (http://www.eathena.ws/wiki)
irc:
#athena in irc.deltaanime.net
------------- rAthena -------------
https://rathena.org/board/ (https://rathena.org/board/)
https://rathena.org/wiki/Getting_Started (https://rathena.org/wiki/Getting_Started)
irc:
#rathena in irc.rizon.net
------------- Hercules -------------
http://hercules.ws/board/ (http://hercules.ws/board/)
http://hercules.ws/wiki/Getting_Started (http://hercules.ws/wiki/Getting_Started)