If at least 90 percent of your sales are swiped through the terminal, you can qualify for a lower discount rate. For a small additional charge, a built-in printer is also available. Meanwhile, you can choose a state-of-the-art refurbished terminal that offers identical features to Charge.com's new terminals at a much lower price.

Once you decide that a Paynet Systems credit card merchant account is the right solution for your business, the application process is easy. Over 95 percent of new merchant accounts are accepted, and approval generally takes place in less than 24 hours.

Since American Express cardholders generate so much revenue for businesses, you might expect that accepting AmEx cards through American Express merchant accounts would be more costly than taking other credit cards. But this is not the case. In fact, businesses that accept American Express do not pay an annual fee, monthly minimums, an online application fee or third-party processing charges.

The Merchants Payments Coalition is a collection of almost 30 associations representing retailers, supermarkets, pharmacies, convenience stores, gas stations, Internet merchants, and other businesses that accept credit cards and debit cards.

When looking to compare fees among various merchant service providers, be aware that the presentation of fees may not be as clear cut as outlined above. Also, different rates may apply depending on the type of card used, which is based on both the card association, such as Visa or MasterCard, and the type of card, such as a reward credit card or debit card.

You also want to be aware of the lag time (anywhere from one to five days) that it takes for you to receive your customers' money. While some credit card processors have more efficient fraud-checking systems, others attempt to squeeze interest from the reimbursement provided by the credit card companies before depositing the funds into a merchant's account.

When you compare various merchant account services providers, nonprofits should weigh all the various costs, ranging from the one-time to the ongoing. These costs may include one-time fees for setting up your merchant account, a monthly account fee, transaction fees per item and a discount rate that is a percentage of the transaction amount, as well as indirect costs such as the time needed for staff to enter credit card data.

In either case, or whenever a merchant or consumer gets a call where the other person's identity cannot be verified, the best thing to do is to hang up. A quick call back to the police or credit card company can verify whether they were in fact responsible for the earlier call.

Avoid using wireless networks when sensitive information is involved, since outside hackers can access wireless features on a laptop. Also, invest in encryption, so that you will not need to let clients know if you lose a laptop or are the victim of a breach.

Some gas station owners have tried to find a way around the system by lowering the per-gallon price for purchases made with cash, which may be the only way consumers can benefit from using cash over plastic.