Apple has made available iOS 6 for you to download and upgrade the OS for iPhone 4S, iPhone 4, iPhone 3GS, iPad 2 and iPod touch (4th generation).
However prior to upgrading, there are a few things you’ll need to do:
Update iTunes to “10.7″:http://support.apple.com/kb/DL1576
Update your Mac OS to “Mountain Lion 10.8.2″:http://support.apple.com/kb/DL1580 or “Lion 10.7.5″:http://support.apple.com/kb/DL1582
“Backup”:http://support.apple.com/kb/HT1766?viewlocale=en_US&locale=en_US your iOS devices
Download all the updated apps that supports iOS 6
Do note that backing up and then restoring from the back up will probably takes you an hour or so…depending on how much stuff you have on your iOS devices.
Also note that some features of iOS 6 is “not available”:/2012/09/ios-6-feature-availability/ for users in Singapore and also certain features are also not available on older models (eg. Siri is only available with iPhone 4S).
Lastly here is a “comprehensive review”:http://www.macworld.com/article/2010065/review-refined-ios-6-highlighted-by-stunning-maps-overhaul.html from Macworld on all the new features of iOS 6.