How to unlock iPhone 4 to another carrier?

How do you unlock iPhone 4 to another carrier?

4s is better.

You can't.

A recent court decision made it a felony to unlock a phone to make it work on another carrier… All the boot loaders and tools that were used in the past are pretty much gone…

Depends on your version of iOS as well as the baseband the phone is running. May or may not be possible depending on the status of both.
Could also pay $20 & check http://chronicunlocks.com to guarantee an unlock, factory unlock.

@Mike: 1. That order is currently under debate in Congress & 2.concerns phones bought on or after the 26th January. Not every one.

I unlocked iPhone 4 by using Remote Unlocking Service. I got this service at very low cost from the site http://www.theunlockarena.com/apple-iphone-4/rs16wp9/ here they ask me to provide the IMEI number of phone, Country, Network provider to which it is locked. After unlocking from iPhone 4 to another carrier, I can able to use any GSM network Sim card on my phone freely. This method does not requires Jailbreaking. This is safe and secure method. You can also use this service to unlock your iPhone 4.

If you want to unlock your iPhone 4 from any network, then you can visit http://www.simpleunlocking.com/apple-iphone-4/rs16wp9/ .Here they provide remote unlocking service to you. Then you can follow the free instructions from http://www.mobileunlockguide.com/apple-iphone-4 and unlock your iPhone easily.