One of the best technique I have ever seen as a user/customer is being able to do the entire call to action without having to log in / fill out forms. eg: if y

One of the best technique I have ever seen as a user/customer is being able to do the entire call to action without having to log in / fill out forms. eg: if you're going to sell me something, try to convert me into a longer time customer / account holder AFTER you've sold me a product. It essentially means creating accounts on the fly based only on an email address.