• Merchant Account Providers
  Merchant account providers represent a bank and offer a variety of products and services that enable you to accept credit cards as payment from customers.
  
  
• Third Party Merchant Services
  They accept credit cards payments on your behalf in exchange for various fees and percentages. You won't need hefty setup fees.
  
  
• Banks
  If you have been in business more than two years and have good credit, you may ask your local bank to get the lowest possible discount rate.

• Internet based processing (Real-Time) - most widely used for online merchants
  With this mehod, after customer enters in the credit card information, the card information flows to the processing center/payment gateway.
  
  You will be able to complete sales of merchandise quickly. Real-time online processing is ideal for sales consisting of software downloads or e-mailed electronic publications. It is also well-suited for a wide variety of relatively small ticket items
  
  
• Software processing (non-Real-Time or manual)
  The manual method requires that you collect order and credit card information from a secure form and then enter the credit card information by hand using your computer and a software program.
  
  This method is ideal when you have to ship ther merchandise or to start delivering the service after a while. You will be able to assure your customers that the credit card transactions won't be completed until the merchandise is ready for shipment.
  
  An alternative procedure, mainly used for higher ticket items, is to have the credit card transaction "pre-authorized" when the order is placed and "post-authorized" (also called a "forced sale") when the goods are ready to be shipped.
  

Click here to read about Real-Time Processing