Take a look at your current phone and try to find out if it is one that uses GSM (Global System Mobile) technology. T-Mobile and some AT&T phones are equipped with this technology, among others. If you are buying a new phone make sure that GSM technology is integrated.
Most cell phone service providers electronically ‘lock’ the phone so that it can only be used with their service. There are obvious reasons why they choose to do this – in particular, to force you to pay what are usually very high roaming charges when you take your phone out of their network and use it elsewhere in the world.
Fortunately, this locking is reversible. With some phones, it is possible to simply enter an unlocking password code into the phone and it is immediately then unlocked. Other phones need to be connected up to a special unlocking data terminal.
For $5, you can get the codes from thetravelinsider.info.
You will need a country-specific SIM card to buy pre-paid minutes for the country in which you are traveling. You can buy pre-paid minutes from telestial.com. The company will send you a SIM card that you use to replace the current SIM inside your phone.
If you have valuable data on your SIM card you can get a SIM Backup and Saver Unit, this will help you transfer all your date safely from one phone/ one SIM card to another.

