[Sony Xperia S, Acro S, Ion] SXUsr:
The process of tinkering with any Device can seem a like a daunting process for New members but it's really quite simple so long as you read

EVERY WORD

of a thread describing how to Modify your Phone you shouldn't go far wrong.​

So you've just received your new XPERIA Phone and want to get it Updated, De-Branded, Rooted, Unlock the SIM & Bootloader, Flash a Custom ROM, Theme or simply Repair your Phone, well hopefully everything contained here should help with all of that, but as most XPERIAs are similar in their workings this is wrote as a general reference, so a link may take you to a page in the Ray section for example but it will/may still apply to you and what you're trying to accomplish. So lets get started...

References:

[GUIDE] Android Dictionary!!

The Flashtool, Updating, Unbricking & De-Branding:

PLEASE NOTE:

If you have Un-Locked your Bootloader

DO NOT UPDATE

Over The Air (O.T.A) or

YOU WILL BRICK

your Device. If you have Bricked then see THIS thread with how to Restore your Phone.

{RECOVER SOFT-brick}[2012 XPERIA's]Recover ALL 2012 XPERIAs from SOFT-brick

[Remote Support] Fully Repair Dead Xperias Arc/Neo/Play/X10/X8/W8/Mini/MiniPro ALL

The Flashtool is simply what it says on the tin, it's a tool that flashes Firmware to your device in a similar manner as SEUS or PC Companion does except the Flashtool requires .ftf files which can be downloaded from your devices General or Development forum. This is generally the preferred method for Repairing your Phone if SEUS or PC Companion aren't an option or you just prefer not to use them. You can also use the Flashtool to flash a Generic .ftf to your device which will remove any Operator Branding from your device.

This video by BlueChipJ explains the process of using the Flashtool...

[YOUTUBE]Keo61Zffh5Q[/YOUTUBE]​

...or you can use (specific Phones only) the Official Sony Flash Tool. See maxio1998's thread for more info - [TOOL]Official Sony Flash Tool | Unlocked Devices

References:

force update by editing build.prop

How to install Flashtool on Ubuntu

How to backup your Sony Ericsson Xperia firmware using Update Service and the FlashTool

[YOUTUBE]bB77gWRUI_A[/YOUTUBE]​

Rooting:

UPDATE: One click root [4.1.B.0.587 /.431 /.562 ] All 2011 Xperias

- What is rooting and why should I do it? The pros & cons of Android rooting

Rooting methods for the XPERIA line of Phones has constantly changed from apps to Pre-Rooted ROMs and Kernels. A Google search of "root -insert device name-" should help to find the specific method for your Phone but the following link is well worth reading - [How-To] Rooting guide for 2011 xperia devices

[YOUTUBE]Rjv71b9QcZE[/YOUTUBE]​

References:

[Arc/S] [PRO] Root for 4.0.4 ICS Update [4.1.B.0.431+4.1.B.0.587]

Root MANY ANDROID! [Upd: 18.12.2012]

[ROOT+BB+CWM] ICS and non rootable GB build

[ROOT][NOOB GUIDE][for unlock BL] For Official ICS 4.0.4

[HOW-TO][FTF] Root and CWM with the latest 9.0.1.D.0.10 firmware

[ROOT&MORE]Xperia 2012 line Flashtool + prerooted system.img + Sony fw FTF + addons

[Tutorial]Root.Xperia 4.0.4 ROM [all h/m(dpi)] | 4.1.B.0.431

[YOUTUBE]7EpkrCq1gfM[/YOUTUBE]​

Bootloader & SIM Unlocking:

PLEASE NOTE: The ONLY WAY to Sim Unlock your Phone is to PAY for it, so do some Googling and read which services have been recommended in the past.

PLEASE ALSO NOTE:

If you're Phone was manufactured AFTER a certain date, 12W11 (look under your battery for a similar number) then the Testpoint method no longer works, and People who have had Phones returned from a Service Centre are reporting that they can no longer unlock via the Testpoint method either.

- Know Your Android Bootloader - What it is and Why it Matters

There are three ways to Unlock yours, the Standard/Official method (For SimFree/Un-Branded Phones) which is explained HERE, (PLEASE NOTE! - You loose DRM when using the official method but not with the TestPoint) but if your Phone came from a Carrier then chances are (99%) you won't be able to use that method. There is a simple method of checking if you can or not which you'll find HERE.

Standard Unlocking:

[YOUTUBE]LRH3pC7MhEA[/YOUTUBE]​

Then there is the TestPoint method...

TestPoint Unlocking:

[YOUTUBE]k5upgfMqNNU[/YOUTUBE]​

Two members - Alejandrissimo or Jinx13 offer a Remote Service which isn't free, but cheaper than anywhere else on the net, and when you take in to account you will also SIM Unlock and retain DRM using the Remote method it's worth it.

References:

[Tutorial] Relock bootloader!

SE Bootloader Unlocking v1.6

[Tutorial] Unlock Bootloader.Test Point | For Newbs

[Tutorial] Xperia S/P/U/Sola Bootloader Unlocking & Relocking

[REF]Booting/Unlocking Xperia 2011 series: What's under the hood?

[Guide] Unlocking bootloader on operator branded phones via Omnius

Fastboot, Custom ROMS & ClockworkMod Recovery:

- Custom ROMS for Android Explained And Why You Want Them

[YOUTUBE]dUsA9HxZjJE[/YOUTUBE]​

In the Development Section you will find a variety of Custom ROMs, some require you to have an an Un-Locked Bootloader and some don't, it's usually stated in the thread title if it's required or not but modding your Phone with an unlocked Bootloader is much simpler. Most ROMs usually come in .zip format which require ClockworkMod (CWM) to install them.

You can find a great Guide HERE that will show you how to use Fastboot which is the method used for installing Kernels required by certain Custom ROMS.

Got a Mac? - [GUIDE] Set up ADB and Fastboot on a Mac easily (With Screenshots!)

- What Is ClockworkMod Recovery And How To Use It On Android

To use CWM on an XPERIA then it's recommended to unlock your Bootloader because then you can simply flash Custom Kernels that come with CWM pre-installed, it's also safer imo because it's separate from the system, but if you haven't unlocked your Bootloader for whatever reason then you're going to have to use [APP]/[RECOVERY]x-Parts [CWM Installer] [Version 7.0] 29/6/12 which is installed to the Phone's system, although it's less effective should you accidentally wipe your system while trying to flash a new ROM as you won't be able to access it.

References:

[TOOL] Fastboot and ADB helper v1.0

[4Noobs] Flashing a Custom Rom & Kernel Using Fastboot

[How-To] Install custom kernel/rom on 2011 xperia device

[HOW-TO]Set up Android SDK/ADB/Fastboot on Ubuntu Linux

How to Flash boot.img / kernel.elf / kernel.sin using flashtool

[TOOL][FASTBOOT] QuikIMG - A frontend for fastboot [0.2 beta]

[Tutorial] How to install CyanogenMod 9.0 on xperia 2011 devices

[TOOL] RecoverX - Recovery installer for almost all android devices

[RECOVERY] TWRP 2.3 for all your Xperias. (downloads + DIY howto)

Fastboot & Flashboot ADB Driver installation on Windows 8 Guide for Sony Xperia Users

How to Install CyanogenMod on your Xperia (bootloader unlock, fastboot, Google Apps, etc.)

[YOUTUBE]O52IeX93Jek[/YOUTUBE]​

Modifying & Theming:

To be able to install full themes that you're going to find in the Themes & Apps section of your device then at the very least you are going to need to be Rooted as you'll need to be able to overwrite, delete, add files to the system, and default theming on the XPERIA line is quite limited. If you choose to use a Custom ROM such as FXP's CyanogenMod 7/9/10 then you have the benefit of using the ThemeChooser so you can download themes till your hearts content from the Play Store.

Adrian DC has released a DefaultThemes Customizer which you can download from HERE, or you can learn to modify apks yourself and mod your Phone to your own liking.

References:

[Guide/Tools] Simple APK Modding

[MOD] Get the Android Emoji Font from JB on ICS

★All System Apps And Details [15/12/2012]★

[Application] HomeCustomizer for SONY ICS ROMs

[TWEAK] ICS Specific Tweaks of XPERIA MOD ROM

[GUIDE] How to remove "data traffic" icon from notification bar

[TWEAKS/SCRIPTS/DOWNLOADS]~ BEST TWEAKS EVER ~

[APP]

Show Off S 2.0.1 [for via "Sony Ericsson Xperia arc" in fb]

[How-To] Make custom bootscreen/bootlogo (image to rle)/(rle to image)

[TUT] How To Center The Clock On The Statusbar..And Move Other Icons As Well!

[How-To]Removing Battery Percentage,Adding Toggles,Battery Circles to Statusbar

[GUIDE] how to make battery % icon remove AM/PM ,remove battery text on the left

Other Useful Info:

[Tutorial] How to use swap for those who can't create swap file in swapper 2

[MOD]Term-init & Zip-init: Enable Init.d for Any Phones w/o Need of Custom Kernels!!!

[GUIDE][APP][2.2+] Sixaxis Controller - Play Games w/ PS3 Sixaxis Dualshock3 Gamepad

[DEV]Chroot-Linux on Xperia Devices Locked/Unlocked Bootloaders(Debian,Ubuntu,BT5up)

[MULTI-TOOL] StudioAndroid

xda AutoDEODEXTOOL (xADT)

[TUTORIAL] Making Flashable ZIPs, EDIFY Script, ZIP Signing & Key Creation

[Tool][AIO]Universal Android Flasher v1.40 b (ROM-dump,adb,Fastboot,build.prop,etc.)

[TOOL][GUI][10/8/12]AndroPlatina Utilities v2.0|Megaupdate|Latest-ROM Dumper,GUI,More

Development:

[Tutorial] How To Logcat

15 Apps for Programming on Android

[Guide]Complete Android ROM development and essential tutorials ~~ By Nero Young ~~

Android - Chef Central

dsixda's Android Kitchen

(GUIDE) How to port ROMS!

[Tutorial] How to build a ROM?

[TOOL]Aroma App Package Creator v1.1

APP][DEV] Update me [ROM MAKER] - 2.0.3 - PUSH NOTIFICATION

How to build a Linux kernel and flash it to the phone

[GUIDE] [Xperia P/S] How to unpack/pack the Sony 2012 kernels

[DEV TOOLS] - Pack & Repack Boot.img Files - for Windows USERS

[GUIDE] How to make your regional firmware an .FTF file

[Guide] How make a FTF of stock firmware from SUS files

[GUIDE]How to make a rooted flashable rom from ftf file[FOR ALL XPERIA PHONES]

[tutorial] | how to extract system.sin

[tutorial] step by step method to extract ftf file from ics [ics]

[Tool] Yaffey - Utility for reading, editing and writing YAFFS2 images

[TUT]Make Your Own Vanilla IceCream Rom [Custom Rom][Lightweight,Smooth&cool]

[DEV + HOWTO] KangXperiaProject - AOKP for Xperia (tutorial to compile from source)