You've read all about the GTD system, and you've decided to go for it. Now what?
There's at least two approaches for getting started. The one I did was to start big. I allocated a whole weekend and did nothing else than kickstart my GTD system. I cleared my dining table to use as a giant inbox. I collected every bit of paper, every unopened letter, every unread book and magazine, every appliance that needed fixing, and everything else that I needed to do anything about, and put them on the table.
When I found large items that were too big for the table, I wrote down what it was, where it was, and what I needed to do about it, on a separate piece of paper, and put that on the table instead. A proxy like this is as good as having something in your inbox, when the thing is cumbersome.
After that, I took several A4 pieces of paper, and titled them "Next actions", "Projects", "Someday/maybe", and "Waiting for". These were my lists. I decided to start with pen and paper, rather than a fancy sofware solution, to avoid getting distracted by technology. Pen and paper is about as simple and reliable and uncomplicated as you can get. When you start your GTD system, keeping it simple means you're more likely to make it work. You can try complicated tools later, but initially avoid the trap of getting lost in finding and selecting optimal tools.
Then I started processing the inbox table. I picked the topmost item, and thought about it, and decided what to do. A lot of things went straight into recycling or garbage, which was nice: I no longer needed to have them in my life at all, and this made me feel better. Any stuff that I had lurking about was stuff that potentially demanded attention from me, and even if it only actually did that once a year, with a thousand unnecessary things, that's three things per day.
Other things went into my lists. In fact, most things went into my lists. During that first weekend, I did not actually do anything much. I did a few very quick things, such as throw away rotten fruit, but otherwise I suspended the two-minute rule.
After I'd cleared the table, I did the same thing with my computers. I collected all my files and e-mails and bookmarks and so on into one digital inbox per computer, and then processed those. I still kept all my lists on paper, though. As it turned out, my digital life was in much better order so there were rather fewer next actions and projects generated from that.
By Sunday evening all my inboxes were clear, and my lists were long. It was somewhat depressing to have so many things in my lists, but it was a huge relief to know that everything I needed to be on them, were on them.
Over the next few days and weeks I tackled the lists, doing things and sometimes deciding to uncommit myself from things, to get the lengths of the lists under control.
The slow start
A big start may require you to put everything else on hold for a day or several days. A gentler, but possibly less efficient way to start is to go slow. Set up an inbox and the lists. Whenever you have time, go through some of your stuff and put anything you haven't already processed into the inbox, or process stuff already in your inbox. This can be much harder to do than the big start, since you need to keep track of what has and what hasn't been processed yet, but it also means you can continue to function normally while you do it.
You might start with just one aspect of your life. For example, start with your e-mail only. Or your non-electronic mail. Or anything to do with work, or your studies, or whatever. Then expand your GTD system with time to cover more of your life.
Sometimes you have so much unprocessed stuff in your life that you feel you're drowning under it. For example, you might have an e-mail inbox that's several thousand mails long, and you feel you're not ever going to be able to deal with it, there's just not time.
You can deal with it by either giving up, or by taking a long time. Some people have declared an e-mail bankruptcy, where they announce that they've deleted their entire inbox, and if anyone had anything important they should re-send. This may or may not be a good idea, but it does give you a clean slate to start from.
An alternative is to create a new folder, and move everything from your inbox into that. You'll get to everything in there eventually, but keeping your actual inbox clean makes it possible for you to start keeping on top of incoming stuff, since it doesn't get buried between all the old, old stuff. You'll need to process everything in your inbox frequently (at least once a day), and after you've done that, you can process a few things from the old pile too. Eventually, the old pile will be gone.