There's a forum post at xda-developers which details a fairly involved and definitely for the faint at heart. However, do not follow that guide, it's included only for posterity, and there is an easier way to skin your particular cat.
At this point, cue the huge disclaimer that a lot of things might go wrong when doing this, and always be sure to follow the instructions as closely as possible. When in doubt, ask. Also, while this guide probably won't change much between versions of the recovery tool, always read the official documentation first and use this as a handy checklist.
Whiskey Tango Foxtrot is Revolutionary?
Brought to you by the same guys that worked on unrevoked and AlphaRev which have been traditionally used to root HTC devices, Revolutionary is a new S-OFF and recovery tool for next-generation devices. The list of currently supported devices is here.
Okay, what do I need to do?
Download Revolutionary. Versions for Windows and Linux are available.
Windows users: Download and install also these fastboot drivers.
When downloading, also request a beta key. Select your device type, and put in your serial number.
If you are running the stock ROM, your device S/N should be in
Settings->About Phone->Phone Identity->Device Serial Number. If you are running a custom ROM, this number might not be there, so you can either check the box your device came from, or (better) find it on a sticker below your battery. It's a good idea to also write this down somewhere for future reference.
You can find the HBOOT version of your device, in case there are several, by booting it into recovery mode: turn your device off, then turn it on while holding simultaneously the Volume down key and the power button. The HBOOT version should be visible somewhere on the recovery screen.
Okay, now you have everything you need.
Make a backup of your phone. No, seriously, MAKE A BACKUP of your SD card and any application information you'd like to keep. Contacts, SMSes, and everything you can think of. Better safe than sorry. There are free tools on the Market that can help you.
If you are going to install custom ROMs, now would be the time to copy them to the device's SD card.
Extract the Revolutionary archive in a convenient location on your computer, and run the executable (
revolutionary.exe, depending on your platform).
Connect your device to the computer. Remember to enable USB debugging when doing so (
When prompted for the beta key, supply what your key, and then follow the instructions on screen (basically, confirm a few times that you do indeed know what you are doing). It might take a few minutes, and your device will reboot a few times.
It worked, and my phone's not even bricked!
Welcome to the club! Flash a snazzy new ROM like a king, and enjoy responsibly your newly-gained privileges. Some things you might want to do, though:
Before doing anything else, make a backup of your stock ROM from the recovery mode, in case you'd like to restore it later (for example, to take advantage of the device warranty, or when selling it).
If you are only after a root without installing a custom ROM, then you'll also need to install the Superuser application from the recovery. If you'd rather flash a custom ROM, you won't need this, most ROMs also includes Superuser as a part of their base install. For information how to install your ROM of choice, consult the documentation supplied by the ROM vendor.