Given that a lot of us use UniversityOfWalesAberystwyth 's network which is suspected to be routinely logged and monitored it may be wise to use irc on secure connections only. To do this, use a SSL-enabled IRC client such as XChat, mIRC, BitchX, and connect to a server's SSL port. See AberFreeNet for a listing of servers and ports. You can also use any client with stunnel from http://www.stunnel.org.
It is also possible to use the cgi:irc securely at https://www.ivixor.net/cgi-bin/cgiirc/irc.cgi, however this method has not been very well tested.
To ensure end-to-end encryption the party you are communicating with must also be connected via SSL. You can find this out whether this is the case by carrying out a /whois <nick>.
If you want to create a channel where only secure connections are permitted, mode that channel +S