What pitfalls should I be aware of before chosing a company ...
Can someone explain to me what the "discount rate" is?
Thank you

I accepted them in my small business and I can tell you they vary greatly. AMEX is around 3.5%, the cheapest you generally get is about 2.5% but that is if you do the transaction at the point of sale. Also if the cards are benefit type of cards, they carry rewards to the user, the rates that you are charged goes up. I used First National Processers for my credit card transactions. They also sell the machines that you need. They charge a small fee based upon your volume.