Re-keying Electronic Transactions
Once a transaction has received an electronic authorization, never delete the transaction and re-key it. This will cause the transaction to be downgraded and will significantly increase your discount rate for that transaction and your ability to respond to a charge back will be diminished.

Using "Made-Up" Authorization Codes
When an authorization attempt is responded to by a Decline or a Referral, do not make up an authorization code and enter it. Transactions with made up authorization codes will receive the highest possible discount rate and will have no charge back defense. That means that if an authorization code is made up, and the cardholder disputes the charge, the amount of the transaction will be charged back. That is a large price to pay for not calling the voice authorization center.

Settling Transactions Late
With credit card transactions, you can't put off 'til tomorrow what you should do today. Timely settlement of transactions is necessary to assure the lowest possible discount rate. If you put off settlement, you may pay more.