[AT&T, Rogers HTC One X, Telstra One XL] azd9:
I had a first generation Galaxy S and was fairly involved in XDA until I traded it in for an iPhone. A few days ago I bought the One X and I noticed there weren't any guides tailored to Mac users on how to flash custom ROMs from a brand new stock device. So here I go. If I have time and get the permission of the developers of the root exploit I might eventually create a mac program that automates the process. Over time I will also try to improve this with screenshots and better instructions. I take no liability if your phone blows up or if it doesn't work for you.

This is just a rough draft, use at your own risk.

Overview

Root the Device

Install Custom Recovery

Install Custom ROM

Directions

Assuming you are on the latest firmware, 2.20, you have to use the X-Factor root exploit. It should be in the downloads folder that you will download below. I did not come up with this expliot so if it works you should donate to its creator. For convenience I bundled the tools you will need into a single zip file. You can download it here. Place the unzipped folder on your desktop. You will also need a custom ROM downloaded from the Android Dev portion of this forum.

Rooting

Back up all data that you would miss if lost.

Open up settings > Developer Options > USB Debugging

Plug your phone into your computer. Do not mount the drive; just leave it in charging mode.

Move the folder you downloaded earlier onto your mac's desktop. Now open a terminal window and type "cd desktop/htconexmac" and press enter.

Now type "sh run.sh" and press enter.

Press enter again when the disclaimer pops up.

If it works, on your phones screen a message should pop up asking for backup restorations as well as a prompt for passwords. Ignore the password spaces and autorize it. It should prompt you twice.

The phone should restart into "bootloader mode." Press the enter button on your computer once this loads and it should confirm that your new CID is "11111111" if it worked. If it doesn't say that then try again from scratch.

Press enter again and you should get a big block of text copy the whole block including the tags on either side of it. You will need this to unlock the bootloader.

Go to htcdev.com and make an account. Now go to htcdev.com/bootloader and in the drop down box select All Other Supported Models press enter and follow their directions.

Recovery

Close terminal entirely (not really necessary, it just makes things go smoother) and reopen it. Now type "cd desktop/htconexmac" and press enter.

Now turn your phone off entirely and turn it back on by pressing the power and volume down buttons at the same time. You should boot back into recovery mode. This time, use the volume keys to select fastboot

With your phone plugged in and USB Debugging still enabled, type "./fastboot.osx flash recovery twrp.img" This will install the TWRP Custom Recovery. I did not make this, if it works for you I would suggest donating to its developer.

When it is done installing you can turn off your phone and then boot back into the bootloader by holding the power button and volume down button at the same time.

Now scroll to recovery and press the power key. You should boot to a screen with lots of buttons.

Flashing the ROM

Press the button that says "Mount" and then press the button that says "Mount USB Storage." In a moment you should see your phone appear mounted as a disk on your computer. Drag the .zip file of whatever ROM you downloaded to this disk as well as the file titled "gaaps.zip." Once they finish copying press "unmount."

Press the back button to return to the main screen and then press the button titled "Wipe"

Do a factory reset. Press back. Wipe the cache. Press back. Wipe the Dalvik cache. Press back twice to get to the main menu.

Press "Install" and then select the zip file on the ROM you want to install. Press "add more zips" and select "gapps.zip." Finally slide to confirm the flash.

When it is done flashing go back to the main menu and press "reboot" and then "bootloader"

Make sure it says "FASTBOOT USB" in red. On your computer find the folder where you kept your ROM and extract the zip file. Find the file called "boot.img" and copy it into the htconexmac file on your desktop.

In terminal type "./fastboot.osx flash boot boot.img"

When it is completed type "./fastbook.osx reboot"

Your phone should boot with its ROM!