For any business that does a significant amount of credit or debit card transactions, it's important to make sure that your credit card processing fees are as cheap as possible since they can add up to a significant expense.  Your merchant account provider charges you credit card processing fees in order to take the customer's card and do all the work so that the revenue (minus their fees of course) is deposited into your bank account each month.

The best way to keep your credit card processing fees to a minimum is to encourage to pay with checks or cash.  This way, you won't be paying several percent of the transaction to the company in order to process a card.  If your customers are willing to cash or use a check book, this can save you a lot of money and may be the difference between a company that makes money and one that loses money.  If your customers are unwilling to pay cash, you either need to figure how to incentivize them using cash or perhaps not reveal that you take cards until someone asks.  The problem is that most customers these days expect businesses to take their cards and therefore you usually need to take a credit card to make your customers happy. 

When possible, ask your customers to use their debit cards because the credit card processing fees on these are much has than credit cards because the money is taken from their account at the time of the purchase.  Debit purchases can be nice because while the customer must enter their secret PIN code, they usually don't need to sign a receipt.  Credit card purchases will result in the highest fees for you.  Often the worst is an American Express card where the processing fees can be nearly 5%!

It's also worse in businesses where you don't have the credit card in your hand at the time of processing.  This is because when you have the card, you can check the ID of the person using it and be fairly confident that everything is okay. Purchases made where the card is not present such as buying something online or by phone or even when you need to write down the credit card information and input it later are considered riskier by the credit card companies because they are less willing to trust that the transaction is valid, and they can get hurt later if the card turns out to be stolen and the person using it was not the card's proper owner.

Another important factor which can have a huge impact on your credit card processing fees is whether your business has had many chargebacks: a chargeback is when a customer calls the credit card company directly and asks that they reverse a charge you made because the amount is wrong, because they don't remember making the purchase, or even if they are unhappy with the product or service you provided.  You are unfortunately in a tough position because the credit card company is much more likely to side with the customer than you in a credit card dispute.  This means that you should do everything to make a customer happy to make sure that they do not issue a chargeback since this could dramatically increase the credit card processing fees you pay for every single one of your card-based transactions.