Airfare

Wing of Boeing 747, landing in Hong Kong
This article assumes you want to travel on a meager budget. Airfare can really vary around the world. If you are travelling for more than several months, buying a round-the-world ticket can be a good deal. The key is working through the company you're buying from to find the best route. For example, travelling through hub airports like Bangkok or Hong Kong can be a lot cheaper than other cities in the area like Beijing or Tokyo. If you can find some example fares, which use these hub cities, and then modify this itinerary to suite your needs, you can come up with a good fare. There are lots of companies selling consolidated tickets these days. Most are low key and operate out of San Francisco. Airbrokers.com is a good company that's willing to work out complex schedules. Another high profile company is Air Treks, but I find they're expense and inflexible. Buying a multi-stop or "round the world" ticket also allows you to change the dates of your flights for free while on the road. This is a good feeling.

If you're a student or under 26 years old, you are guaranteed at least a resonable price with a student or youth ID card. You can buy tickets through companies like STA/Council Travel*, though there are limited numbers of tickets for these fares on each flight. Going through increasingly popular travel agents like Flight Centre or CheapSeats.com can also bring up good fares.

Looking through airline websites can also be a good way to find periodic deals. Many airlines offer discounts to reward those willing to buy directly from them. So find an airline that specializes in flying to your destination and look them up.

Europe
Virgin
Australia and New Zealand
Quantas
Air New Zealand
Hong Kong and Asia via Taiwan
China Airlines
Cathay Pacific
Northwest
Discount travel in Asian, Europe and the US
Dragon Air
Easy Jet
Southwest

Finally, one should never be afraid to simply ever buy a ticket for the first leg of your trip and book your next connection from there. Though you won't have that feeling of comfort from knowing exactly where you'll be going and when, there's a good chance you'll be able to save some money and keep your options open in case you don't realize what you really want to do until you get there. You should allow this to happen.

*These are, by the way, the same company as of last year. I heard from one of the employees that Council Travel was a much better company before it was acquired by STA. Apparently they had decent benefits and were generally fun to work for.