You can save money AND balance your checkbook much more easily by using cash instead of plastic, or even in place of your checkbook. It's so easy to hand over a piece of plastic to pay for numerous items. Even a debit card doesn't quite drive the fact home that you're spending real money; it's still a piece of plastic. The checkbook might help you be frugal a bit more, especially if you're a zealot for deducting. However, I have found that by taking out installments of cash from the ATM, and sticking to the "cash only" rule, I spend a lot less money.
There's nothing like holding the actual bills in your hand, that reminds you that you're spending real money. You're not just throwing $200 here and $300 there: You have fifteen twenty-dollar bills in your hands (most people don't get fifty-dollar bills from the ATM). You can't help but wince a little when that money leaves your hand, not to mention your purse and your bank account. Even at Wal-Mart, or better yet, an attractive thrift store, a lot of items can add up to $100 or more quickly.
Granted, there are times when you have no other choice but to use plastic, such as when renting a car, or paying for medical expenses or big-ticket items. However, whenever possible, try to use cash. Hey, the little walk from the pump to the booth at the gas station won't hurt you! In addition, it's going to be much easier to balance your checkbook. ATM withdrawals are a lot easier to keep track of than a number of small (or large) expenditures.
If you are doing a budget, you may want to keep track of where your cash is going for a few months, but once you've finished your budget, you should know approximately how much cash you will need for each category, such as grocery shopping, clothes, gas, etc. Leo Babauta, of ZEN HABITS fame, suggests keeping separate envelopes for each category with a set amount of cash. It doesn't even have to be that complicated. I know how much I earn per month, so I know approximately how much cash to get from the ATM for a given period of time. And get this: once you've run out of cash, there is nothing more sobering than having to drive or walk back to the ATM as opposed to flashing a piece of plastic. Plus, you won't be in debt!