Most service providers lock you into a fixed monthly rate that buys you a certain number of airtime minutes and other extra features that you add on. After you pass a credit check, you sign a contract committing yourself to the service for a certain period of time -- usually from 11 months to 3 years. The carriers, in return, offer free or steeply discounted phones and accessories when you sign up.

If you decide to cancel service, it will cost you! Most providers have an early termination penalty. This can range from a flat fee to a charge per month remaining on your contract. Also, if you break your contract, some carriers even make you give the phone back. Some consumer electronics stores levy their own early cancellation fine! It is a good idea to check into whether or not you can get a trial period of service to test out a plan. This gives you a limited window of opportunity to cancel service without any penalty if you find out that a provider just doesn't meet your needs. Otherwise, you'll have to wait until your contract is up to get a new deal from a different provider. There are also month-to-month plans (with no annual contract) that allow you to change the number of minutes and other provisions.

Pre-paid wireless is one convenient alternative to long-term contracts. Like pre-paid phone cards, these plans let you buy a chunk of airtime that you can draw from until it runs out. You can buy service in $25, $50 and $100 blocks. Until recently, carriers offered these plans with little fanfare to those who didn't meet their credit requirements. The plans proved popular with some cell phone users who want to keep a close watch on their cell-phone expenses, however, and now are more widely available. These plans have a number of benefits including:

• No monthly fee
• No long-term commitment
• No credit check required to sign up for service
• No deposit to start service
• Features such as caller ID, three-way calling, call forwarding and the wireless Web are available from some carriers. (There is a per-minute fee that is subtracted from your account balance if you use these extras.)

There is also a downside to choosing pre-paid plans. First, you usually buy the phone without any special discount. The retail price for a cell phone can top $500, depending on the features included! Some other disadvantages are:

• You pay more per minute.
• If you don't use the phone for an extended period of time, you lose the money in your account.
• You can't make collect calls, third-party billed calls, and calls to 500, 700, 855, 900 and 976 numbers.

If you're trying to stick to a budget, you should know that both monthly and pre-paid plans have "hidden" charges. With a monthly plan, these extras are added to your monthly bill, but with a pre-paid plan, they are simply subtracted from your account balance. Examples of these are:

• One-time fee activation fee charged to program the MIN and SID codes into the phone.
• Directory assistance costs up to 99 cents per call
• Per-minute fee charged by land-based phone companies for terminating calls from cellular phones to regular phones (3 to 16 cents per minute). This fee is in addition to what you've already shelled out for your on-air minutes!
• Federal, state, and local taxes and other fees charged for monthly service.