Be a squeaky wheel. Say you want out because the service isn't up to par. (And really, is it?) Then back that up by filing official complaints online with the Federal Trade Commission and the Better Business Bureau. However, if you have no grounds for complaint, then these steps will not help you.
Get a lemon. Get a known problematic phone, complain 3 times, be let out of a contract due to your local lemon law. However, most carriers and manufacturers warranty their phones for one year and will offer alternatives if you continue to have problems. Try a market-based fix. Some companies such as CellPlanDepot.comand Cellout.ca match unhappy mobile customers with people who'd like to sign up, at a discount of course. Some of these sites are free and others charge a nominal fee.
Try a cell-contract swapping service.
You can get out without early the termination fee, but ...
CellSwapper: Free to post. $14.95 if you sell your contract.
CelltradeUSA: $19.99 to transfer a contract. No fee to take over a contract.
Resellular: $14.99 to transfer a contract. No fee to take over a contract.
* There are more but these are the most widely known and respectable services.
Look for your provider to bury changes to Terms of Service with your bill. Quite often providers modify their service plans, much of the time the modification is a benefit. It doesn't matter, this voids the previous contract. Read the small print on those inserts included with your bill, it will spell out that you have 30 days (may vary on where you live) to cancel your contract with no charge simply because they changed the contract.
Get off the grid. If you move and cannot get the same level of service as your previous location, tell your service provider. They're not legally required to cut you loose, but frustrated consumers have reported success. T-Mobile's and AT&T's is to waive the Early Termination Fee if you do not have service in your area. This step may have to be verified with their engineers.
Join the army. If you are a member of the US Armed Services and you receive orders to somewhere the company doesn't provide service they are obligated to cancel your contract free of charge. Keep in mind, you'll have to provide a copy of your official orders. Your base legal office should be able to provide you with free assistance in working with the company. Most carriers will offer a military suspension option as well.
Force them to produce the signed contract. Ask them to produce a copy and mail it to you. This step rarely works anymore, as most retailers do send their paperwork to storage facilities or scan them into databases and can usually pull up contracts and receipts fairly easily.
Shrink your plan. As a last resort, cut back to the bare minimum the provider allows and drop any frills, like picture-messaging. Depending on the number of months you have left, this could be cheaper than paying the early termination fee, which can often run up to $300 per line. However, at some cellular companies changing your plan, even to reduce it, may extend it for at least another year, so do the math first to make certain it will actually save you money.
Dead?? If your cellphone happens to be in someone's name who recently deceased (spouse, Dad, Mom, the CEO/Owner of your workplace) - call and get the service cancelled.
Got a good phone? Consider paying the cellphone contract termination fee with the money you get from an eBay auction of your phone.