What shots should I get if I have never gotten a vaccination before & I want to travel to a 3rd world country?

CDC.GOV. For the most complete and up to date information go to the centers for disease control website at cdc.Gov. There is a link on the website for travelers to all parts of the world.
It depends! Choosing your immunizations for international travel can be complex: where you're going (which countries & in which order), how long you're staying (days, weeks, months?), what you'll be doing (rafting, safari, luxury?), what season, and of course, your medical history, and very importantly, personal feelings about risk (and budget). See a travel medicine expert! find one at www.Istm.Org.
Many are recommended. Travel shots are vaccines that aren't routinely given to people but are given to those who will travel to developing countries that lack high standards of medical care. The meaning of travel shots have been expanded to include shots that are routinely given, such as vaccines for hepatitis a, hepatitis b, measles, influenza, etc... The cdc.Gov website is a good resource on travel shots.