Make sure that as much automation as possible takes place in the back-office. All manual tasks (per sales order) will lead to rising costs and increased possibilities for errors. And if your webshop grows, these problems will also grow bigger.
To rule out payment problems and to run less risk, automatic collection and electronic bank transfer are the simplest and most client friendly. The order can than be processed after receiving the payment.
Make sure the database structure is built in such a way that it allows for easy expansion and without it's fundaments to be changed. That will support easy growth of the webshop.
The back-office should support client access and control. That will save time and money.
Your clients should be able to get easy contact with the organization behind the shop. That will create trustworthiness with your the (potential) clients and a better client satisfaction.
Source: http://www.communicatiecoach.com (in Dutch)