[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] RPelham:
Well ROMs come in many different flavors. It depends on what you like. If you like a pure android experience (with some extras and mods) similar to the Google Nexus devices, I would recommend CM10.0.0-Stable (for a daily use ROM).

CM (CyanogenMod) has more up to date versions, but are very buggy and not recommended for daily use until the bugs get ironed out. The CM10.0.0 is a 4.1.2 based ROM and the more updated version CM10.1 is a 4.2.1 based ROM which is the buggy ROM I mentioned.

If CM doesn't sound like your thing you can view these forums to see other ROMs:

| Android Development

| Original Android Development

If you DO like the sound of CM, you can follow my below steps:

==== WARNING ====

I am not responsible for anything that could happen to your device in the event that your device is bricked or no longer usable. I also advise that you read all stickies on the forum before moving forward with the below steps. These steps are specifically detailed for the AT&T Samsung Galaxy S3 i747 (d2att) phone. If you do not have this phone, disregard the following information:

==== END OF WARNING ====

To install TWRP (which is what I prefer) follow these steps:

1.) Download Goo Manager

2.) Open Goo Manager and grant super user rights.

3.) Press your "Menu" button and select "Install OpenRecoveryScript"

4.) Possibly grant super user rights again and repeat step 3.

5.) Confirm you are sure you wish to install TWRP

6.) Confirm yet again you are sure you wish to install --AND-- make sure the file is: openrecovery-twrp-2.3.3.1-d2att.img

7.) Sit back and wait. Goo Manager will take you to the Goo website and download the .img. It will then reboot your phone and install the image. You can follow the status of the download in your drop down task bar where it is downloading.

Once the image is installed you can confirm by booting into recovery mode by shutting down your phone, then with the phone off press and hold Volume Up, then Home Button and then Power button simultaneously. Once the phone vibrates you can release those keys and you should be presented with a blue screen with the "Team Win" logo.

You can then click "Reboot" then "System" from within the recovery. Your phone will boot up into the system. Download these files if you wish for CyanogenMod CM10.0.0 Stable:

CM10.0.0 ROM: http://get.cm/?device=d2att&type=stable

Google Apps: http://goo.im/gapps/gapps-jb-20121011-signed.zip

Once you have downloaded both of those files, move them to the root of your Internal Storage on your phone.

Reboot into recovery as explained above and follow these directions:

1.) Select "Wipe" then select "Cache" and Swipe to Wipe.

2.) Then repeat with the option "Dalvik Cache" and "Factory Reset".

3.) Once you have fully wiped the device select "Install" and then select "cm-10.0.0-d2att.zip"

4.) You will then get a confirmation, select "Add More Zips" and select "gapps-jb-20121011-signed.zip"

5.) You will then get another confirmation. Then "Swipe to Confirm Flash" and it will go through the process.

6.) At the end it should say Successful and "Reboot" Select "Reboot" to boot into the new system.

If you have any further questions, feel free to ask =)