How does one avoid a bank overdraft?

Bank overdrafts occur when one makes a purchase by check, credit, or other vehicle to access money in one's bank account, but there are not enough funds in the account to pay for the purchase or charge. If the bank chooses to pay the charge anyhow, an overdraft occurs, which typically results in a negative balance, and the bank charging a fee. Careful attention to one's balance and spending habits is the most prudent form of avoidance of overdrafts, however, sometimes banks will give the user an option to not pay overdrafts, meaning that the check or charge will be returned unpaid.