Hello,
Is your online payment system registered with SSL? Actually what happens at online payment system customers enters their credit or visa card numbers during payment. How can they rely on you that you will not misuse this data? So, it is strongly recommend you should register your payment system with SSL and show this security device on payment page. For more information go here www.sslstar.com. I hope it will help your customers to trust on you.

It will depend very much on which type of payment you offer, is your site redirecting your customers to a payment page on your payment service providers server or do you accept credit card payments directly ? Are you offering other payment methods then credit card payment ?

Og I forgot, do you have an SSL certificate on your payment page, and who is the issuer ?

I think I need to know what is your payment system is,I myself also having a payment system that I stated here.and about how to make your consumer confident I think it depends on your presentations.I am sure the use of SSL is required and the use of "anti hacker tools like Mcafee secure seal is standard,but you know it is not enough to get trust ,It need "publications and press release to get the "no popular situations "fixed"