The most expensive part of starting that travel adventure is normally the initial flight to take you to the area of the world you are interested in visiting. For most North Americans it means the flight to Europe or Asia.
Long Haul flights don't have to break the bank. There is many low-budget no frills airlines that takes you between major hub destinations. It's important to read the fine-print and baggage allowances on sites like these, but even mainstream carriers have the occasional seat sale.
It's always best to try and book between big international hubs. If you are flying from North America to Europe look for destinations like Paris, Frankfurt, London or Amsterdam. If you are flying from North America to Asia look for flights to Hong Kong then get another flight from Hong Kong to your Asian destination.
Long haul international flights tend to be booked well in advance, at least 2 months a head of time for saving the most money. Under one month and you will almost certainly pay more than you should. Make sure when you are looking for flights you search each day of the week, you would be surprised how often companies have a cheap flight on the same day of the week, every week.
The only destinations that really seem to be expensive to fly to are African destinations. I find it rather annoying and a bit troublesome. You can get to Egypt for a decent price but most other places are going to cost you.
Personally for long haul flights I would check out the main stream travel websites like Kayak, Condor, Expedia, and Orbitz.
Once inside Europe the world is really your oyster, there are many low-budget airlines between the different European countries. Very cheap fares on air travel even on short notice bookings (under two weeks). Ideally the prices are best around the 2.5 to 4 weeks in advance for booking short flights.
If Asia is what you are interested in there isn't a much better hub airport than Bangkok. You can easily fly daily to almost every other major city in Asia.
