[EVO 4G General] steve19137:
Go to http://revolutionary.io/ and enter your serial code. To find your serial code, take your battery out, and on the white panel, look at the bottom number. It should say S/N: BLAHBLAHBLAHBLAH. You must enter in that valid serial code to get the root to work. Make sure you get a beta key when you click Generate Key.

Unzip the package that was automatically downloaded. Turn your phone back on. Plug your phone in and launch revolutionary.exe. It will ask you for the beta key, enter it at that time. It is case sensitive, so type carefully.

If you are stuck at "Waiting for device...", you have to put your phone into USB Debugging mode (home screen > menu > settings > Applications > Development > check USB Debugging) and install this package: http://downloads.unrevoked.com/HTCDriver3.0.0.007.exe

EDIT: As I have gone through all the posts in this thread, there are various problems that people are having because I didn't make a few things clear, and I apologize. You cannot have HTC Sync installed. It has it's own special drivers that interfere with the revolutionary tool. Uninstall it if you have it. Also, your USB Mode has to be Charge Only. Not HTC Sync or Disc Mode or whatever it is (I can't remember since I have flashed a custom ROM). It has to be charge only with USB Debugging on. Now back to our regularly scheduled programming.

Let the tool run. When it asks if you want to install a custom recovery, choose yes. If it crashes at that point, you need to rerun the tool so it can install the custom recovery. At this point, all you have done is unlock the bootloader and install a custom recovery. To get root (required to backup apps on the phone before installing a custom ROM), you must flash this package in the recovery: http://goo-inside.me/superuser/su-2.3.6.3-efgh-signed.zip

At this point, you have a rooted stock ROM, a custom recovery, and an unlocked bootloader, allowing you to do basically anything you ever wanted to do with your phone. Please make sure that you don't do something stupid to brick your phone. Do your research, ask questions if you can't find an answer (easy way to get flamed: don't search), and enjoy :D

Notes: This tool can only be used with HBOOT 2.16. If you have 2.10 or lower, first, don't even try to use this tool, second, slap yourself for not rooting earlier because there have been root methods for that version for a very long time.

People are wondering why they require you to enter your serial number to generate a beta key. If you took the time to read into what you are trying to do, you would have likely stumbled across this page (http://unrevoked.com/rootwiki/doku.php/public/revolutionary#common_problems_questions) which talks about the required serial numbers. They say that to generate a key, you have to enter your serial number. You need a key so that if problems occur in large batches of devices, they can stop issuing beta keys, therefore preventing root on the phones supported. If you don't want to enter your serial number because you are paranoid, that's your choice. That means you will have to wait for a stable release, which won't require any keys, but that is likely to be a long time, obviously much longer than it took to root this update to begin with.