Getting things done is very simple. Just do the work. That’s it. You have a list of things to do, now go to them.
But Aaron, you say, I need a method! No, you don’t. The only time you need a method to get things done is when you have more tasks than you can do in one day. Now, that might be most of you. It’s certainly me. But having a method just for the sake of having a method is missing the point.
The math is simple: if you add up the amount of time it will take you to do everything on your list, and the total is greater than number of hours you have available today, then you can’t get everything done. Some of the items on your list will have to be done another day. Possibly many other days.
Now you need a system. You have due dates (and ‘do’ dates, too) and an order to the tasks (some come before others). More complexity begs for a system. But your system should serve you, not the other way around.
Don’t “do GTD” just to do it. Examine your needs, and build a system that fits them. Anything more is fluff and the spinning of wheels. And we’ll never get anywhere spinning our wheels.