In your IRC profile setup, don't put your real name in the Full Name field. It is customary to put a silly slogan or motto.
Always set yourself "invisible" or "+i" as shown on the Personal Modes page. Some software prompt you for this in setup.
Never use scripts or special defense software without knowing how to use it or turn it off and on.
Never EVER have your software set to auto-accept DCC files or chat. You can get viruses, hacked, or flooded. Is the risk worth the cost of a few extra seconds and the click of an "accept" button? (No, I don't think so either)
Never have your software set to auto-join a channel on invite. You can end up in a very bad place. Again something very easy not to do.
Never give out your real contact info to strangers.
Try to limit your chat to those networks which offer some sort of channel registration service.
Log everything! Preferably timestamped. it might look annoying in chat, but it's the most reliable evidence.
Remember: NOBODY IS ENTIRELY ANONYMOUS. A Simple /whois will reveal the connection "dns mask" of a user. That mask is like a fingerprint. To report an abuser, all you need to do is e-mail their ISP's support with a log of the incident, along with the dns mask, date, time, and your time zone. They can check their connect logs for the culprit.