But on a serious note, it all depends how creative you get. Find some unsecured wireless, theres your first start. If you do get traced back anywhere its not to you. Change your MAC address, not strictly legal iirc but its easy to do. VNC to a computer on a seperate network and then go through proxies via there, more creative you get the harder it is to track. End of the day if you've REALLY pissed someone off then theres only so much you can do before the games up.
^ This.
Due to the very natures of the way TCP/IP works it is very difficult to totally anonymise your connection (if not impossible), all you can do is to make it as hard as possible for someone trying to trace you to get at the logs off of the devices you bounce through.
Ideally what you actually want to do is crack someone's secured wireless (piece of cake, you'd be surprised), then spoof the MAC address of one of their own devices, then to all intents and purposes you looks like a known device on some random's network. If you then use that spoofed connection to route through TOR and then through a bunch of proxies etc, making sure that you jump between countries that do not have very good relations with each other (for example, go from a proxy in Iran to a proxy in Israel, when their trying to backtrace the Iranian authorities will have f**k all to do with the Israelis), you make it as difficult as possible.
If you were doing it properly, you would use non-persistent USB boot images on "borrowed" hardware you do not own, connecting via someone else WiFi .
Then again, this does sit on my desk :evil:, so I do take security fairly seriously, so you wouldn't catch me doing anything like that of course.