Both international and domestic tickets are better when purchased in advance, not only do you get a good price, but you will get a better flight(connection). In most cases for international travel 3-6 months in advance and for domestic tickets 2-4 weeks in advance purchases is recommended. 

Yes, for any international travel out of the United States you need a valid passport. 

Since each country has its own rules and regulations about obtaining a visa, we recommend you contact the embassy directly to find out whether you need a visa or not. For embassies addresses and locations please visit www.embassyworld.com. 

Yes, we strongly recommend you buy a travel insurance since most tickets are nonrefundable once purchased and if you need medical coverage while you are traveling it's a good idea to have insurance. To learn more please visit www.travelguard.com 

Some countries require a valid health certificate prior to entry. To get more information please check www.cdc.gov/travel