Thanks James and Michele for your questions. I'll answer them as best I can.
1. Where are you heading to after South America?
Here are my plans for the near future, in brief:
After Brazil, I plan to ride the "death train" across the pantanal and into Santa Cruz, Bolivia. I know I've been to Bolivia multiple times already, but there's still some more adventurous stuff I want to do there. Yes, Bolivia is that great of a place to visit.
When I'm done with Bolivia, I'll head past Lake Titicaca and into Peru for the fourth time (Peru is another great country to visit). There's a couple highlights there that I still haven't gotten a chance to do (most notably the Huayhuash Circuit).
Next, I'll go north to Ecuador, where I only spent a week last time around. During my time there, I plan to go to the Galapagos Islands. When I get back to the mainland, I'll cross through Colombia and Venezuela and go all the way down to Angel Falls, which will complete a near circle of most of the continent that I started when I went to Roraima in Venezuela last November.
After that I will probably jump over to Cartagena, Colombia and get a boat around the Darien Gap and into Panama. From there, I'm just a hop, skip, and a jump (through eight countries) from the US!
I don't really know how long all of this will take, but I almost certainly won't be back in the US until 2008. Of course, these are just plans. Who knows, maybe I'll end up on a yacht to some remote Pacific island. After this trip, I don't have any major plans other than to get a job and start saving money again.
2. I'm very interested in traveling and want to do pretty much exactly what your doing. How do you even start about doing this?
For starters you need money. I'm sure you're quite young since you're in high school, which is a good thing in this case because you have lots of time. I know it sounds way too simple, but the key to saving money is to spend less than you make. When I graduated from college I had almost nothing, but soon I got a job that paid good money. Saving was no problem for me because my lifestyle was simple so I didn't spend much. When I thought I had enough money to take a few years off, I quit.
If you want to go to college, you'll probably have to put off traveling for awhile (unless you study abroad - an excellent option), but you should be rewarded when you graduate with a higher-paying job than you would have had if you didn't go. Either way, eventually you'll have a job and will be able to start saving.
Your friends will be in the same situation as you, but they'll probably start buying big houses, fancy cars, expensive clothing, etc, but if long-term travel is really your goal, you shouldn't do any of this (one possible exception is buying a house - maybe). Don't go into debt, start putting aside whatever money you can, and eventually you'll have enough to go. While you're doing this, doing some research will help keep you motivated to save.
3. Did you just buy a ticket, fly down there, and that was that?
Pretty much, yes. But looking back, I wish I would've done a little more research on some specific destinations. For the most part, I got my timing right by hitting Patagonia in the summer, but since then I've done some major backtracking that has cost me time and money. The reason I didn't do any research was because I wanted to be spontaneous, but I guess there has to be a balance between spontaneity and knowing where you're going. You should at least try to get to your destinations at the right seasons.
The good thing is that if you don't know much about where you're going until you get there, you'll probably meet a lot of people who will give you good info once you get started. Everywhere I go, the locals and other backpackers tell me where they've been and what's good to see and do there. This is a better source of knowledge than any book can give you.
4. I'm very interested in Africa-do you suggest that to be a good place to travel around?
I think anywhere is a good place to travel around. I haven't been to Africa, but I've met a lot of people who have gone there and enjoyed it. Many people rave about countries like South Africa, Madagascar, Kenya, Morocco, Tunisia, and Egypt just to name a few. I recently met a guy from Gabon and his surfing photos looked amazing. It will be a good idea to learn some French if you want to go there. French is widely spoken in 29 countries in Africa.
A lot of people will tell you that Africa is too dangerous, and of course there are some countries that are so war-torn you definitely shouldn't visit them (Sudan, for example). The problem I have with taking other peoples' advice about visiting another country is that in most cases, that person has never actually been there. Almost everyone at home told me South America was dangerous, yet most of those people have never even left the US. Most of the places I've visited have been very safe, and even the more dangerous ones can be safe as long as you use your head. To figure out where exactly you want to go in Africa (after all, the continent has over fifty countries), I'd start reading travel books and web sites based on African travel.
Another option if you really want to go to Africa but don't have money is to join the Peace Corps. It's a big commitment, but I've met many workers who have enjoyed it. And after all, Africa probably needs more help than any other region of the world.
Email me if you have more questions. Considering the amount of time I've spent traveling, I obviously think it's a good thing, and am willing to help you reach your travel goals as well.