Taking $20 off a $160 phone bill doesn't sound like much, but it's a start. You can also reduce cell phone costs by attacking the usage charges that vary every month. Here are a few tips.

Keep an eye on the minutes: Most companies offer several ways for you to learn how many minutes you've used up so far on a billing cycle. For example, Verizon users can dial #646 for a free text message.

Block music downloads and applications: Frequently, kids discover that they can download music and play games on their phone, but they don't consider that it will show up on the phone bill. And anyone can accidentally access the Internet and incur a charge.

Shop for better rates: Comparing plans is easy, but moving an entire family to a new carrier can be heartbreakingly expensive. If you added family members to your current plan at different times, each phone number may have a different contract end date. At no one time would you be able to move everyone to another carrier without incurring multiple termination fees. For a family of four, those charges could run into hundreds of dollars.

The solution? Wait until everyone's contract runs out before you upgrade anyone's phone or change the plan. Then everyone will be in sync.