Do this and you’ll manage your checking account successfully

Managing a checking account isn't rocket science but it's not basket weaving either.  (No offense meant to basket-weavers.  I tried to weave a basket in eighth grade art class and it ended up looking more like a Frisbee.)

But managing a checking account boils down to one key skill:

You have to know that the money is available before you make a payment or a withdrawal.

This can be illustrated in a number of ways:

• A deposit isn't in your account until the bank says it is. Bank and credit union policies differ.  Some banks or credit unions will trust you until they can't:  If you go to an ATM or a teller and deposit a $200 check, they may give you use of the money immediately.  Others may place a hold on the funds until the check clears.  The bottom line is that it's up to you to know when you can use those funds, either by verifying your balance at the bank, or through a call-in service, or online.
• A withdrawal or a payment has left your account when the bank says it has. Checks clear a lot faster than they used to, and automated clearing house (ACH) withdrawals can happen very quickly.  It's therefore wise to assume that there is no lag between when you make the payment and when it's debited to your account.  For recurring debits like a mortgage payment, it's best to earmark those as “debited” at least a few days in advance of the expected payment date.
• Relying on a linked savings account as a buffer will cost you. If you have a linked savings account, your bank will probably offer as a service the ability to dip in automatically to funds there if your checking account goes negative.  This saves bounced check fees and non-sufficient funds (NSF) fees, but banks charge for each transfer from savings.  This is the “slap on the wrist” charge.
• Relying on more extensive overdraft services will cost you more. This is essentially a loan from the bank that carries a per-transaction fee.  If your account goes negative, and you don't have sufficient funds in a linked savings account to cover the charge and the fees, then if you're opted in to this overdraft service, the bank will intervene, make the payment anyway, and charge you a larger fee for covering your six on that transaction.  This goes beyond slap on the wrist to spanking.
• There's always the big guns:  non-sufficient funds fees and bounced-check fees. The savings-transfer fees and overdraft service fees mentioned above are less costly than NSF fees.  These are not only assessed by the bank, but by the merchant that you didn't pay.  All because you didn't know that the funds were unavailable when you wrote the check.
• Your “balance” may not be your actual balance. Some banks may include the amount of your overdraft service protection when you ask for your balance.  So, if you have $100 of protection through an overdraft service, and your actual funds are $500, then the balance might report as $600.  It's still up to you to know that you really have only $500.
• Know what happens when you pay with a debit card at a gas pump. I don't pay with debit at a gas pump, but I do know that stations put a hold on some amount above and beyond what you'll actually pump, just to be sure that they're paid.  Be sure you understand how this affects your balance, and for how long.
• Know the other rules of your account. Do you have a minimum balance?  A maximum number of transactions per month?  Teller fees?  Paper statement fees?  All of these and more can affect your balance.  Be sure you understand them.
• Do not expect the bank to hunt you down the second you go into the negative. It may take a few days for the notice to get to you.  This happened to me a few years ago.  My checking account got low, and the savings transfer kicked in on one transaction, along with a $5 fee.  By the time I got notice of the first fee (sent through the mail, not even at first class rates), I had already made three more transactions, at $5 apiece.  Of course, if I had kept more careful track of things, I wouldn't have done it in the first place.  Nonetheless, it was $20 later before the bank brought it to my attention.

These are specifics, but if you always know your actual available funds before you make each and every payment, things will go fine.

Update: A special thank-you to Money Crasher for featuring this post as an Editor's Pick in the Carnival of Personal Finance!