Visas & Fees
Sadly, the world is not one big happy borderless family. Which means that when you go from country to country you may have to deal with visas & fees to enter. Sometimes you are not required to have a visa or a fee to enter if you are there for tourism purposes, and under a certain number of days. For instance, Canadians are allowed to enter Thailand without a visa or paying a fee as long as they are there as a tourist for 30 days or less.
Depending on what country you are from and where you are going the requirements to enter will change. Make sure that this is one of the first things you look up before heading to your destination. Sometimes Visas can take weeks or sometimes (but rarely) months to obtain.
Here are some quick links to research visa requirements for citizens of: