There is a good guide on what you need to know here www.wisegeek.com/what-are-unlocked-cell-phones.htm
You should be able to get a good used unlocked cell phone from any store that specializes in cell phones. They are hard to come by but you can find them. Another way is you can try craigslist and see if anyone has one on there and make sure it works before you leave.
The best place to buy cheaper sell phones that are unlocked and ready to buy are E-bay. You should always research the seller before buying anything to make sure everything is legit.
Any of the major cellular companies' SIM card should fit into a blackberry. After you have bought a SIM card from a cellular company, all you should have to do is place it into the blackberry and activate it.
Before buying a snowmobile, you should consider the costs and the brand and also the manufacturer.
Before buying a used Toyota, you should know if the car was involved in an accident. You should also know the mileage on the vehicle.
I will assume you do not mean the "Slide to Unlock". Unlocking your phone's cellular plan is probably what you meant. Having your phone unlocked means you have the ability to get cellular service, but without need of a contract. Unlocked iPhones cost $450 more than their contracted counterparts. Your phone also becomes unlocked when your 2 year contract ends. This is why selling your old iPhone after 2 years can actually get you a net profit.
Before buying a notebook, you should be aware of the amount of space needed vs what is offered, and what the prices are for competing companies.
Before buying garage doors, you should contact a home contractor and have him or her come out and determine what kind need to be purchased and the value.
The answer is probably yes. The company you're buying the phone from should be able to tell you for certain.
Before buying a laptop you should always keep in mind you budget. You must also decide what it ill be used for work or play.
know the style
Some things your should know before buying houses to rent are as follows: know the expected amount of rental income, the annual expenses of the rental, and any risks of buying the rental.