The T-Mobile Galaxy S3 Android 4.1.2 update is now in the process of being rolled out to customers. The update brings Android 4.1.2 Jelly Bean as well as a host of TouchWiz features. This update will be available for download over-the-air, which will be available until June 16th, and through Samsung Kies as well. Your device should notify you that an OTA update for it is available. Back in January T-Mobile rolled out an over-the-air build T999UVDLJC update for Galaxy S3 which featured minor improvements and enhancements. The device needs to be running this build before it can be upgraded to the latest Android 4.1.2 firmware.
Apart from the Android OS update, features such as Multi-Window, Samsung Gallery, Easy Mode, Blocking Mode, Auto-pairing with NFC, Paper Artist and Sound Balance are on-board. It also brings enhanced Camera options for taking better photos and videos. To install this latest software update, make sure that your device is not rooted, it has battery over 50%, has a decent data connection as file size is 168MB and that you have the latest version of Kies installed, if manual update is your cup of tea.