Whats Your System? (Not sure how to technically add subscribers for some situations)

Hi,

I've been a WF member for quite a while now and learned a great deal of informaiton. I'm really putting most my effort into list building and getting my systems in place and set up correctly. While I know how to build a list, how to build a squeeze page etc, there are some situations that I'm unsure how to technically get someone on my list.

Let me give you an example:
I have a product I want to start selling, we will call it My Main Product. How do you guys typically sell the product and get someone on your buyer's list. Do you have them pay then after they pay they are taken to a thank you page with an Aweber opt-in form. Once they confirm, they are sent the download links? Do you have software/membership software that handles this? If so, what is it?

Another scenario:
Lets say I have a product or course, doesn't really matter. I typically sell it for $XX but I'm willing to let affiliates sell it for 100% commissions just so I can get the buyer on my list. I'm assuming the setup is the same as above, except that I use my affiliate software to give the affiliate the sale...everything else is done the same? What software do you guys use for this?

I am already selling some products, getting subscribers, and making sales but I know it can be done a lot more efficiently. I'm hoping some veterans can shine some light on how they're doing it.

Thanks in advance everyone!