[AT&T Samsung Galaxy S 4 General] Branzino:
Steps

a. Root your device

Scary, isn't it? I was in the same boat and really hesitated to do it. However with no other option available it may worth a try. It does work well and give you good control of the phone. Worthy in my opinion, especially when it allows you to do what you want to do.

a1. If you are new to rooting your phone like me, some background reading may help:

http://www.kingoapp.com/help/android-rooting.htm

https://sites.google.com/site/tomsgt123/all-videos/samsung-galaxy-s4

a2. Watch this video as a preparation and confidence building:

http://www.youtube.com/watch?v=uii_mYm8IGE&feature=youtu.be

a3. Root your device using the steps here. It echoes the steps in the video. Even though it is made for the Verizon model, it works on AT&T too:

http://xdaforums.com/showthread.php?t=2565758

b. Modify the tethering file:

b1. Follow the steps in the post. It works:

http://xdaforums.com/showthread.php?t=2535141

b2. Pay attention to the mount /system as RW mode step. It is missing in the original post:

"I was not able to rename files or copy until I change 'Mount R/W'.

To do this, you click on globe/phone on top left corner.

Scroll down to "Root Explorer" and hold for a second or two.

When you let go, a pop-up screen appears. Click on Mount R/W,

and change "/system" from OR to RW."

http://xdaforums.com/showpost.php?p=48950107&postcount=87

c. Verify tethering works

c1. Use your favorite tethering app, it should work. Just disregard the AT&T Popup (click OK).

And if you don't use any tethering app before, rest at ease. Your phone's native Wifi and USB tethering also work. That maybe the best part as you don't need to purchase any "unlocked" version of those apps. Just go to "Settings->More networks->Tethering and portable hotspot". Turn on Mobile Hotspot and you can use Wifi tethering as usual.

c2. Or while at the same screen, connect your phone to the laptop with a USB cable and enable "USB tethering". Your laptop will automatically install a USB driver and you will be connected to the internet via USB. This option works especially well when all you need is connect one laptop to the internet. It not only saves the battery of your phone by not using Wifi, but also charge your battery while tethering!

c3. Stil not enough? How about make your laptop a wifi hotspot? Follow the steps here:

http://lifehacker.com/5369381/turn-your-windows-7-pc-into-a-wireless-hotspot

This way, you charge your phone while tethering using USB, your laptop is on the web, and others can connect to the internet via the Wifi hotspot on your laptop. It is a win-win-win situation :)

d. Finally, if you don't want to be annoyed in the future and redo all these again (which may or may not work anymore as they may close the door), turn of AT&T Software update. Follow the steps here:

Stopping AT&T Auto Software Update

Download and install "App Quarantine ROOT/FREEZE" from Play Store.

Open the app and go to settings by tapping on the wrench icon at the top right of the screen.

Uncheck the "Hide system services" option.

Go back to the app and select "AT&T Software update".

Tap on the lock icon on the top right of the screen.

It may ask you to enable the USB debugging.

Feel safe from AT&T's new attack

http://xdaforums.com/showthread.php?t=2387577

Again, many thanks to those who put the information together, and to those who tried it and proved it worked. You guys are great! Happy new year and happy tethering!