[Verizon Samsung Galaxy S III] Bleelas:
I'm ready to start rooting/flashing!

There is an excellent guide stickied in the development thread here http://xdaforums.com/forumdisplay.php?f=1672 (big thanks to droidstyle). However, many of us forget what it's like to be a COMPLETE newbie and to someone who has no idea about anything, even that guide can be a little intimidating. You can follow the instructions, but may not understand what you're doing. The steps to take to start out with are:

1. Make sure you understand what I've written above. Make sure you are comfortable with the possibility of bricking your phone.

2. Root your device. As I said above, this is simply gaining root/Admin/whatever you want to call it access on your phone. In and of itself, it does NOT alter the ROM or kernel. However, there are many different ways to obtain root and some of them DO alter these things. The easiest and safest way to root (IMO) is to use Noxious Ninjas excellent tool. http://xdaforums.com/showthread.php?t=1792342. If you like it, I encourage you to donate or at least "Thanks" him. It works by taking advantage of debugfs permissions to get the su binary (remember this from above??) onto your phone with permissions set so you can run it. It therefore doesn't change ROMs or anything else. You won't lose data, apps, or anything else. It just sneaks su right onto your current setup.

3. Install a custom recovery. This will allow you to do all the fun stuff I talked about above. I recommend installing EZ-recovery from the market and flashing CWM 6.0.1.0.

-- Install EZ-recovery

-- Under the "Recovery" heading, click the Recovery radio button and select CWM 6.0.1.0

-- Click flash

4. Backup everything as if your life depended on it. This means backing up your NV/IMEI as shown here http://rootzwiki.com/topic/32397-tutorial-imei-backup-nv-with-qpst-us-variants/ and making a nandroid (see above). You can restore a nandroid backup and you'll be right back where you were before flashing or changing things around. You should also back up texts, anything on your internal sd card, and programs SEPARATELY from a nandroid (see below) so that you can easily replace them after flashing a new ROM. The steps to making a nandroid are (similar steps to restore):

-- Turn off your phone.

-- Hold down volume up, home, and power until recovery appears.

-- Use the volume rocker to go to "backup and restore" and hit the power button

--- Select backup and then select the external or internal SD card

5. Unlock the bootloader. See the aboot partition discussion above for what this means. You must do this seperately from flashing ROMs and kernels. Refer to this thread http://xdaforums.com/showthread.php?t=1839791 and give appropriate thanks! A warning...if you mess up your aboot partition, there's really nothing (that I know of) you can do to revive your phone besides sending it to someone with JTAG.

A quick note about backing up apps. Personally, I use Titanium backup because I've used it forever...and I think it's a great app. I'm not going to go into details, because it's not too tough to do a few basic things with it and because I want to stick to things that will help prevent bricks.

You're now ready to start flashing ROMs!

As a precursor, there are ROMS that are based on TouchWiz modified Android from Verizon/Samsung and there are ROMS based on AOSP (e.g. CyanogenMod). TW roms need a TW kernel and AOSP roms need an AOSP kernel. Until you get comfortable with everything, I would stick with TW, but that's just my opinion. Don't worry, you'll get comfortable pretty quickly.

Also, some roms come with kernels and will flash the kernel to your boot partition in addition to flashing the ROM to your system partition. Some ROMs don't come with kernels. If the ROM you choose comes with a kernel, that's great. If not, you'll still have the kernel you are currently running and you need to make sure there are no incompatibilities with your new ROM. ALWAYS ALWAYS ALWAYS read the OP of a rom you want to flash to find out kernel information as well as how to install the rom and anything else you may need to know. The general steps to flashing a ROM are (remember to read the OP for specifics):

1. Backup apps, data, call log, contacts, messages, etc. My program of choice for much of this is Titanium Backup available on the market. If you choose to use it, buy it as you'll use it a billion times.

2. Download the ROM you want and check the MD5

3. Place the ROM on the root of your SD card. Do NOT unzip it.

4. Reboot into recovery and make a nandroid backup

5. Wipe data/factory reset and wipe cache. Wipe it more than once if paranoid. People sometimes talk about wiping Dalvik cache. It's an option in your recovery, but it's not necessary IF you did a factory/data reset because the Dalvik cache is on the data partition which is wiped in the reset. You may want to wipe the Dalvik cache for some other purpose however.

6. Go to "install zip from sdcard" and select the ROM you want

7. If you want/need to flash a kernel, install that zip from the sdcard too.

8. Reboot and restore all that you backed up

If you want to flash a kernel without flashing a ROM, all you need to do is reboot into recovery, make a nandroid, wipe cache and Dalvik cache, and install the zip from your sd card.

Remember:

-- ALWAYS read the OP before installing anything

-- backup before making changes

-- verify MD5 checksums

-- wipe data and cache when flashing a new ROM (unless told not to by the ROM dev...sometimes referred to as a dirty flash)

-- NEVER accept an OTA (having a custom recovery should block OTAs anyway)

That's it for now. If people like this or have requests about other good noob topics, I'll consider adding to it. If not, then screw you! :)