Many people will get bored with the Carriers providing the iPhone from getting unlocked. Everyone knows that all the carriers using iPhone locks the iPhone and gives it on a contract basis of two years. Do you believe that you are free after contract period?
The hidden truth in it is that they wont officially unlock your iPhone till the end of five years from the purchase and this is not assured yet by the carriers.
Well, We are users. So we will look for unofficial unlocking the iPhone.
Before starting the process, there are some notable stuff to be remembered.
- Check your OS current version.
- Check the firmware version of your OS (which is really important) and see whether it is possible to unlock with the applications currently available in the market.
- Choose a particular stream/method of doing the unlocking.
- Look for the reviews, posts and response regarding the unlock and make sure that you will get enough help when needed.
Are you ready to start? 
I prefer unlocking via redsn0w and ultrasn0w which will be really simple to do.