Knowing how to boot the Samsung Galaxy S3 into recovery mode manually gives the users power to make several changes to their handset. In recovery mode, users can do a factory reset, install manually downloaded updates, wipe the cache clean, and gain access to other options that users cannot normally access using the phone's menu. 

Similar guides from sources like the Android Central forum, Android Pit, and Android Geeks share the same steps. Here's how to manually boot the Galaxy S3 into recovery mode: 

Step 1: Turn the S3  off. This could be done easily when the phone is working, but if the device is doing a boot loop, or if it is frozen and the S3 won't respond when the power button is pressed, the user may need to pull the battery to turn off the device. 

Step 2: Once the device is off, press and hold the Volume Up, Power, and Home buttons at the same time. Release the Power Button once the Samsung logo appears. 

Step 3: Continue pressing down the Home and Volume Up buttons until the recovery menu appears. When this menu appears, it means the S3 is on stock recovery mode. 

Step 4: Once the S3 is in stock recovery mode, the user will see a menu with items highlighted by a blue bar. The Power button serves as the accept / OK button. From this window, users can clear the cache partition, install updates from external sources or via ADB bootloader, do a factory reset, or simply reboot the system. Stock recovery mode also allows users to troubleshoot problems that the S3 may have. 

Step 5: The S3 usuallly reboots after a process is completed. The Reboot Now option appears after a process is completed in Recovery Mode. Just select this option and click on the Power button to accept. This will restart the phone into normal boot mode. 

A word of advice for those unfamiliar with the S3's Recovery Mode: changes made under Recovery Mode may affect the performance of the phone. This is why when a user selects an action in the Recovery Mode menu, they are asked multiple questions several times before confirming the action. Do not get annoyed by this - it is a safety feature meant to protect the users from accidentally making permanent changes to their system.