Feature Requests

Here you can order a new plug-in functionality.

Is it possible in payment and shipping methods in checkout , not be preselected any method so the customer have to manual select any of the payment method?

Yes.... but It's a bad idea.
If customer refreshes the page he will lost his preselected settings.
Don't do it.
You can order shipping and payment method.
How does plugin work?
If customer selected shipping method before nopcommerce remembered it and plugin used this old selected settings.
  
It's a bad idea. You should use native nopcommerce logic.

is it possible to guide me to do this?

The problem is that customers just press checkout without change payment or shipping methods.

You can add JavaScript code... but you can get to know if customer opens the checkout page first time or refreshes the one.
It's bad idea.