[Sprint Samsung Galaxy S III] fergie716:
So this is a guide on how to make a flashable zip (a zip file you put on your SD and install it via a custom recovery). I'm going to assume if you want to make a flashable zip it's because you modified an app (or found one on the internet but it's not meant for our device) so I'm not going to explain how to modify an app or anything like that but I will post some resourceful links

*I own a laptop and use Windows so all the information is based on that, please adjust information if you have a different OS. You can also do all of this using a file explorer and text editor on your phone

So, I've attached a flashable zip that is meant for our devices and uses our mount points. I will go through some situations on where you can/should use it.

First, download the attached zip and extract it (7-Zip is free, use stock settings).

Within the extracted folder you will find data, system, and META-INF folder. Go to the base of the end of the META-INF folder structure and open up the updater-script file (I use Notepad++). This dictates what gets "flashed" and the text you see while in recovery. After you open it pay attention to these lines:

-This will display text inside recovery, you want to enter text within the parenthesis and quotations, so if you wanted your text to say

Your text in updater-script would look like

And don't forget that semicolon!

OK so that's how you enter custom text that you would see in recovery. Next important lines you'll see are

This mounts your system (/system) and data (/data) partitions so whatever apps/jars/xml's/boot animations/fonts/etc you flash will end up where you want them to go (as long as you have the appropriate file structure; continue reading on that)

So you want to keep those within your updater-script, even if you are just flashing a system app it will not hurt anything on your set up if /data is mounted.

The next important lines are

This now extracts whatever you have in your /system and /data folders within your zip into your system so it's important to make sure that you're satisfied with whatever you have in those folders prior to flashing

The last two lines,

simply unmounts the data and system partitions after everything is flashed

Just a note, this should not be used if you are flashing an entire ROM, I will update this with an updater script for this.

So after you modified your files and signed them correctly place them in their appropriate locations. For example, if it is a modified SystemUI.apk you will make a file structure like /system/app/SystemUI.apk, then select both the META-INF folder and system folder, right click and scroll to 7-Zip and select "Add to Archive", use stock settings and select OK. Place your zip on your internal or external SD and flash in recovery

This should be used for modified system files (apps, jars, files (init.d scripts, xmls), boot animations, apns, init.* files, etc), or data files (themed Facebook, Twitter, apps you download from Google Play)

IMPORTANT NOTES:

-If you are going to flash something, make sure the name of the apk's/jar's/files match the original apk's/jar's/files (example: if you are on a TW ROM and flashing a modified Messaging app you or someone else made, the correct name for that app is SecMms.apk). In that example, your apk would be in /system/app/SecMms.apk

-If you are flashing a modified Google Play, Gmail, YouTube, etc (themed, hacked, etc) make sure the app you flashed isn't in /data/app/ so make sure you delete apps that were automatically updated by going to /data/app/ (using a file explorer with root permissions) then flashing it.

-MAKE A BACKUP! Just in case. You can always make a backup of whatever apps your flashing by copy/pasting them onto your SD then make a flashable backup zip just in case something goes wrong

-It won't hurt your system if you have empty folders in your zip. If you're lazy just don't delete the empty /data or /system folders in my example

-Here are some general file locations of common apps that you may be flashing:

Google Play (/system/app/Phonesky.apk)

Messaging App (Touch Wiz) (/system/app/SecMms.apk)

SystemUI (statusbar) (/system/app/SystemUI.apk)

Framework-res (Android Framework) (/system/framework/framework-res.apk)

Gmail (/system/app/Gmail.apk)

Bootanimation (/system/media/bootanimation.zip)

LINKS:

apktool (make sure you Google how to set-up apktool in accordance with your OS)

-Notepad++ (what I use to modify xml's and updater-scripts)

-7-zip (I personally use WinRAR but this is free so...)

-File Explorer (FX) (what I use to create/extract zips on my phone)

**I will add more in the next few days, really late here so I'm going to crash