1. Use mIRC as your IRC program. It is easily configured to maintain your anonymity. Note that the following info applies to all IRC clients, not just mIRC.
2. NEVER give out your real name, phone number, address, or ANY personal information to a stranger on IRC.
3. Use a gender neutral nickname. Use something like Kingfisher, Watcher, Taker, etc; something that doesn't identify you as male or female.
4. In the setup of your IRC info, change your personal info. Instead of entering your real email address, put a fake address (like email@example.com) or simply something like "Not available".
5. Under the Identd section of Setup, DO NOT put in your real userid. This will anonymize your IRC logon address. For example, if I were to use my real userid, someone could do a /whois on my nick and see this: firstname.lastname@example.org. They could use this to derive my email address which is email@example.com. If, however, I use a fake userid in the mIRC setup, something like "nobody", a /whois would give them this: firstname.lastname@example.org. Now they won't be able to figure out what my email address is.
6. Set your personal mode to invisible. This will make you more difficult to find if someone is harrassing you. Simply type in /mode yournickname +i. You will not be literally invisible on IRC. Users on the same channel as you still see you there. You will, however, be invisible to a user who does a /who or /names. A /whois nick, however, will show your user information and the channels you're on.
7. If you are being harrassed by a user, change your nickname frequently, set your personal mode to invisible (see above), and place the harrasser on ignore. Ignore is set with this command: /ignore [username or address]. For example, /ignore warthog or /ignore *!mjack@*.neosoft.com.
8. NEVER NEVER NEVER accept a DCC chat or file send from someone you do not know or trust!!! This is the cause of 95% of all IRC security problems. In the mIRC DCC options section, set DCC Chat and Send to IGNORE ALL. Never have the Auto Get option checked!! This is how trojans and viruses can spread.
9. NEVER NEVER NEVER do something a user asks you to do if it sounds fishy or you don't know what the result may be. For example, if a user asks you to type in /DO blah blah, DON'T DO IT!! They may very well be able to gain total control of your system if you do.
If you follow these simple measures, you should have no concerns about security on IRC. Remember, don't trust anyone you don't know on IRC. Be careful, and be safe!!