You will need a copy of fastboot which is part of the Android SDK.
I know there is a touch of double posting here but I wanted to make a thread so users can find all the info they need in one place.
I found the Telstra XT925 particularly tricky to work with and the below method worked flawlessly where others failed.
Give it a try and let me know how you go.
Apologies as a new poster I can't supply the links, but most of you will know where to look.
Motorola drivers from website.
(1) While the phone is fully loaded, go to Settings -> Developer's options and enable "USB Debugging".
(2) Now power off the phone completely
(i) Either by holding the power button for 5-10 seconds or pressing it once and hitting "power off"
(3) Once powered off, hold the power button + both volume buttons at the same time for 3 seconds
(4) You'll see a bootloader menu, you have literally only 3 seconds to select an option
(5) Using the volume buttons +/- go to select "AP Fastboot" then press the middle "rocker" button that's nest right inbetween the volume
button to select it.
(6) If successful, you'll be taken to fastboot screen with white writing on a black background.
(7) Install the Motorola USB drivers (these are readily available from the Motorola website)
(8) Install the Android SDK
(9) Download the Clockworkmod recovery image
(10) Download the Clockwordmod Super User zip
(11) Once the USB drivers are install, plug your phone in, it should detected as a ADB device.
(12) Copy the CWM image into the folder where fastboot is located in the SDK (normally \Android SDK\sdk\platform-tools
(13) Open up command prompt as administrator
(14) Change to the SDK platform tools folder where both fastboot and the CWM recover image is kept.
(15) type in "fastboot flash recovery FILENAMEHERE.IMG"
(16) Wait a few seconds, confirmed successful
(17) While the phone is still on, you can copy over the Super User zip file onto the SDCARD on your phone.
(18) Power off phone.
(19) Repeat the power + volume buttons process but then this time select "Recovery" and press the rocker.
(20) This should load into the Clockworkmod recovery system, go to install zip. Then select the SU zip file.
(21) Install, then reboot.
(22) Let phone boot up, you should now have root access.