[Galaxy S III General] ManCityFC:
A guy I know asked if I could let him know how to Root and Flash ROM's, so I did him a guide. It turned out to be a pretty comprehensive guide and I guessed others might find this useful too?

DISCLAIMER!!!!! This WILL void your warranty, so take that on-board, although you can de-root the phones and put them back to their shipped state

theoretically

. If your phone ends up a pretty brick, and Samsung aren't interested, that ISN'T my fault. THIS IS ENTIRELY AT YOUR OWN RISK! THIS GUIDE SHOULD BE ACCURATE, I HAVE READ IT OVER AND OVER, BUT READ THE COMMENTS BELOW TO CHECK FIRST. IT'S YOUR PHONE!!!!

First Some Handy App's:

ROM Manager has Custom ROM's that are popular and it can advise when new versions become available. It's a more automated way of flashing ROMs and good for new flashers! : https://play.google.com/store/apps/details?id=com.koushikdutta.rommanager&hl=en

Nova Launcher is an improved version of the Stock Jellybean launcher and allows you to backup your home screens, therefore you don't have to start from scratch everytime you flash a new ROM: https://play.google.com/store/apps/details?id=com.teslacoilsw.launcher&hl=en

Titanium Backup is a pretty (not entirely) essential app that backs up all your apps, and the data associated with them, i.e passwords, game save files, username. Basically the app will be frozen as it is when you leave it. https://play.google.com/store/apps/details?id=com.keramidas.TitaniumBackup&hl=en

ES File Explorer is a File Manager which also has the options in settings to allow it root access to the system files on your phone. This is handy as you will no doubt understand the more you use it. It can also display the MD5 of a ZIP file that you download. https://play.google.com/store/apps/details?id=com.estrongs.android.pop&hl=en

https://play.google.com/store/apps/details?id=com.riteshsahu.SMSBackupRestore&hl=en This will backup your text and picture messages to your SD Card. Handy!

https://play.google.com/store/apps/details?id=com.riteshsahu.CallLogBackupRestore&hl=en This will backup your Call Logs....if you are bothered.

Now down to the Nuts and Bolts! Let's Get Rooting and Flashing!

1) Root and Recovery Install:

You root your device following the instructions in this http://xdaforums.com/showthread.php?t=1703488 post. This gives you Superuser access to your phone and allows you to change the boot options of your phone. This will install Clockworkmod Recovery. Clockworkmod Recovery replaces the in-built recovery that the OEM installs and allows you more flexibility to alter your phone. If you struggle to get into Recovery, then there is a key-press combination that does it when you switch on your phone and there is also an app in the Play Market called "Reboot to Recovery" that will allow you to do it, but you need to understand how to get into Recovery from a cold start just in case you have issues. Most custom ROM's will have it on the shutdown menu of the phone anyway, and once you install a custom ROM and install ROM Manager, then you can access it there anyway. It sounds a bit daunting, but its really simple once you understand how Clockworkmod, or any other custom Recovery works. READ CHAINFIRE'S THREAD PROPERLY BEFORE YOU START - THEN READ IT AGAIN!

2) Titanium Backup & Nandroid:

You will hear people refer to Titanium Back-up's and Nandroids. This is basically a full back-up of your ROM. A Nandroid backs up the exact state of your ROM so you can restore it back if you ever have problems or just don't like the ROM you have flashed. The first thing you have to do when you have rooted your phone is do a Nandroid. In Clockworkmod you will see in the menu's "Backup and Restore". Back it up, this will place it either on your internal SD or the external Micro SD Card (you can choose, it's faster on your internal SD but the file will be large. Over 1GB+ isn't unusual as this will back up all your apps and everything associated with them.) Nandroid, nandroid, nandroid. Do it all the time. You can always delete them in Clockoworkmod or through a file manager - if you don't need them later. Nandroid, DO A NANDROID! Then, reboot into your stock ROM and DO A TITANIUM BACKUP! You can also backup your SMS and Call Logs, too. Don't get over excited and forget. DO A NANDROID and DO A TITANIUM BACKUP! You get the picture!?

3) Custom ROM files and other flashable files:

ROM's, RIL's and Radio's are generally mostly .ZIP files (Google them all and work out what they do! - YES DO THIS - IT IS ESSENTIAL) and are flashed in Clockworkmod Recovery by using the menu item "Install Zip from..." Don't try to uncompress them yourself or it won't work and most files come with a MD5 checksum code. This will verify the .ZIP file is perfect and not corrupted. ALWAYS check your MD5 before you flash. ROM Manager will do this automatically, but if you download a ROM from XDA the author will usually supply the MD5. If you download the ROM ZIP to your phone, ES File Explorer has a function to display the MD5. USE IT!

4) ROM Manager and Titanium Backup:

The two best apps for Android (in my opinion anyway), and you do NEED to buy them really, not essential, but they make your life much easier. ROM Manager has the most popular ROM's and will notify you about updates. The most popular and probably the best custom (or usually the most stable) ROMs are by Cyanogenmod (Google it) and CM9 is their Google Android AOSP (Android Open Source Project - Again Google it and understand it) based on Ice Cream Sandwich and CM10 is still in development, but is their new ROM based on Jellybean. Keep your titanium back ups up to date BEFORE you flash a new ROM then you can put the apps back on in the exact state you left them on the old ROM.

5) Kernels, Radios and RILs (Radio Interface Layer) and Firmware:

These can be flashed in Clockworkmod generally, are sometimes essential, and can improve the performance of you device, but be careful, flashing these can brick your device if it goes wrong or the download is corrupt in some way. Check the MD5 religiously and make sure your battery is full so your phone doesn't switch off mid way through. Kernels are usually OK, but firmware still scares me now. ALWAYS check that what ever you are flashing is for the INTERNATIONAL or UK SGS3 if that is the phone you are using. Do NOT flash another version, their hardware is different and it will brick your phone.....not sure....ask on XDA Developers, nobody will flame you for checking!

6) Gapps:

With most ROM's, you will need to flash the GAPPS.ZIP package to have it automatically restore your photos, contacts and wireless details. So don't forget to do this whenever you flash most custom ROMs. The Gapps ZIP contains important apps like the Google Maps, Play Store, Calendar, Contacts, Camera, Gallery (where you find the Picasa Pics from your PC), and will log your phone into Google, so it's pretty essential.

7) Some other tips.

A) Titanium! (I KNOW, BUT YOU WILL KICK YOURSELF IF YOU DON'T)

B) Nandroid! (I KNOW, BUT YOU WILL KICK YOURSELF IF YOU DON'T)

C) READ THE THREAD AND THE OP BEFORE YOU DOWNLOAD A ROM AND FLASH IT.

D) READ ABOUT THE BUGS IN THE ROM AND DECIDE IF YOU WANT IT.

E) DON'T ASK DEV'S FOR ETA'S - YOU WILL BE GROWLED AT. THEY DO ALL THIS FOR FREE!

F) PLEASE, PLEASE, PLEASE, PLEASE DON'T MOAN AT ME IF THIS BRICKS YOUR PHONE. THIS IS A GUIDE, IF ANYTHING IS INACCURATE THEN NO DOUBT SOMEONE WILL COMMENT BELOW, SO THIS IS A GOOD OPPORTUNITY TO REVIEW TIP C! ABOVE!!!!

F) Always wipe your Cache and Dalvik Cache first, when you flash a new ROM.

G) Read the OP - Some phones need a full factory reset before you flash them. READ THE OP!!!!!

Good Luck. :good: