Standard Online Sales Sequence

The sequence in brief

1. Ka tirohia e ngā kiritaki tō ipurangi rārangi pukapuka
2. Ka tāpirihia e ngā kaihoko ngā taonga ki tētahi kaata hokohoko
3. Ka haere tonu te kiritaki ki tirohia atu
4. Ka tatau te pūnaha utanga a taake hoko, if any.
5. Customer pays through a kuwaha utu (or one of other payment methods)
6. Ka whiwhi te kaihokohoko i tētahi whakamōhiotanga ota a payment reciept mā te īmēra
7. Merchant ships the goods.

From your customers perspective

It is helpful to view things from your customers perspective, this is how it might proceed from their point of view 

1. The customer may click a product classification link first
2. Ka rapu, ka tirotiro rānei te kaihoko i ō hua
3. Then click on a product title for more information
4. Click on the "buy" button to add this product to their shopping cart
5. Change the quantity and press "click update"
6. Continue shopping perhaps adding additional items to their cart, or...
7. Enter a delivery address
8. Tax and shipping charges are automatically calculated, if any
9. Enter remaining order details (you may collect information about the order such as size or colour) 
10. They the choose their payment method (an order will then be emailed to you the merchant)
11. The customer then completes the payment by their chosen method (If the customer choses "credit card", then a secure form will appear to collect credit card details)

After you have received confirmation of payment you can then ship the goods

Once you have set up your shopping cart system it is a great idea to navigate through the above processes. 
Is it smooth and enjoyable?  Are their any changes you think could improve it? 
Testing and becoming familiar with your own system will enable you to understand and thus effectively communicate with your customers