If you were one of the many people who lost the ability to WiFi tether using your Galaxy Note 3 after AT&T's N900AUCUCNC2 Kitkat update, here's a way to get tethering back. You do not have to be very technical to follow these steps, but you need to be intimate with the settings of your phone and the settings within apps, know how to download and install apps using APK files, and be adventurous.
This is the procedure I followed that worked well for me on my Note 3. It will probably work for other phones as well. Disclaimer: in rooting your phone, you accept and assume the risk of bricking. If you want root, it's probably worth it, but before you start you should Google "recover from softbrick" and read several articles to make sure you are familiar with the contingencies, and you should make a full backup of your phone--all your apps and files--before starting.
Get your tethering back:
1. First, you have to root your phone. Note 3 on N900AUCUCNC2 is rootable using TowelRoot. Go to http://towelroot.com, download the APK file, install, and root.
2. Optional step: you can now get tethering back partially (in a way that will work for PC and Mac laptop clients and iOS device clients), by using a tethering app like Barnacle Wifi Tether. The Play Store will report that the app is not available for your carrier, so you have to go to http://szym.net/barnacle and download the APK file directly to install it. The Wifi network Barnacle creates is an "ad-hoc" wifi network, so unfortunately Android phones and tablets will not be able to join it. But it works well for iPads and laptops.
3. To restore full wifi tether functionality, get the XPosed Installer. Download and install the apk file from the website, then run the app and use the "Framework" option to install. This will install the XPosed Framework. Reboot. After XPosed is installed and you have rebooted, run the Xposed app again. Use the "Download" option to search for and download the "X Tether" module. After you have installed the "X Tether" module, reboot again.
4. Voilà, you are done! Native tethering works again on your AT&T Note 3.
Do you hate the "Volume Warning" message that you get every time you try to turn the sound up on your Note? Solution: Use the XPosed app (above) to download the install the "NoSafeVolumeWarning" module. No more annoying warning!
Did your apps lose the ability to write to the external SD card after the Kitkat update? Now that you have root, you can fix this issue using the SDFix KitKat Writable MicroSD app. Do it.
Enjoy your newly restored WiFi tether and drop me a comment if this helped you.