Let's take a step back for a second. Way back. How about we look at a map of the Earth:
If you look closely, you'll notice these big land masses called Continents. These things are big enough that you could probably travel around on one of them for an entire year and not see the whole thing. Better still, many of them are connected to other continents by land. And they have major cities with international airports conveniently spaced at intervals that will take you to wherever you want.
Now imagine you were to pick one of those cities at the edge of a Continent. Say, Cape Town, Beijing, Quito, Cairo or Mumbai. Suppose you booked a one-way ticket to that city, and let the rest of your year unfold from there. Public transportation in most parts of the world is ubiquitous and cheap. You can get nearly anywhere for nearly nothing if you are prepared to go slowly. Ask anybody that's done a year on the road, and they'll tell you that moving slow is the best way to go.
There's no reason that you need to plan more than one flight before you leave. Heck, if you live in Europe or the United Kingdom, you don't even need to do that. The rail line that you take to work will get you all the way to Hanoi if you want. There are people here on Blogabond that have done just that!
The Hard Part
Here are two things to keep in mind that make life more difficult for those traveling without a fully booked itinerary:
Coming Home
At some point, you're going to get tired of traveling. No, honest, you will. You're going to miss your couch. You're going to miss your friends. You're going to want to cook yourself a simple plate of spaghetti, made with that sauce they sell at your local store, and without having to sit in another little noodle stand and look like a tourist.
That's ok.