The iPhone 4 comes out this Thursday, but if you have an iPhone 3GS, you're in luck because many of the same features that come with the new iPhone 4 will be available as a software upgrade for your existing phone.
To get the new IOS 4, just plug your iPhone into your computer. Launch iTunes, and with your iPhone selected, just click "check for update." This might take a few minutes and be sure to back up before proceeding with any OS install.
With the new update installed, there are some cool features you should look out for like wallpapers, unified mailboxes and multi-tasking. With multi-tasking you'll be able to do things like listen to streaming music while browsing the web. To activate it, just double press the "home button." The new OS also comes with iBooks, so you can either download thousands of free titles or buy books straight from the iBookstore. Finally, with all these great features, you may have pages of apps and they can get a little disorganized. You can now drop apps on top of each other to create folders. There are dozens of new features.