Given that the release of new firmware for the iPhone is usually a bit of an event and widely discussed in many places, you’re not likely to be surprised by its release. However, if you’re not sure whether you have the newest iPhone firmware, the process of checking (and installing the update, if one is available) is quick.
Begin by syncing your iPhone with your computer.
NOTE: This article covers updating iPhone firmware only by connecting to iTunes. If you're running iOS 5 or higher, you can update wirelessly. Learn how to do so here.