Learn to say I don't know. Practice how to gracefully say "Thanks for asking about that. I don't know but I will look into that." Do it to a mirror, make it look like it's your right to not know something, not a crime or even a weakness. After the meeting, go check the facts and then follow up with an e-mail.
Google it right there. It's getting more and more common and socially acceptable for anyone just to whip out a handheld device (smart phone, iPad, etc.) and Google it. If you're not sure about that, do ask "I don't know but would you mind if I search for it now?" Search phrase like "
GDP [Country's name]" will actually result in a nice trend graph in Google, like this one for Vietnam. It would take less than 5 seconds; much shorter than time taken by people to apologize.
Prepare some fact sheets. If your work is heavily related with countries, consider printing out some fact sheets like the one on CIA the World Factbook and bring that with you. Similar devices like tip sheets or cheat sheets for basic information like formulas or acronyms will also be useful. The process of preparing them can also serve as a revision.
Use bookmarks and highlighter. If you are carrying some reports with you, use those write-on bookmark stickers to mark the potentially useful charts and tables.
Ask yourself why, for 5 times. While preparing your major arguments, you may consider a technique of asking yourself why for 5 times. For example, you have picked Haiti as your target country, why? It's a poor developing country, why? Because its GDP per capita is only US$820, why is that low? It's at 157th as of 2007. So on, so forth. This technique can help you think about unexpected questions, and also come up with strategies to deal with the "So what?" questions.
Knowing small details is not as important as knowing the big picture. Contingent on the last point, for research (in my opinion) it's more important to know the big picture: rationale, theory or theoretical framework, pros and cons of methods, validity and reliability of the results, and what these all add to the literature or application. While planning for the research meeting, it's most crucial that you having given these components a good thought and be able to justify your interpretation and decision. Random statistics can come later.
Recalling small details is not as important as discerning pattern and anomaly. As the use of mobile Internet browser becomes more prominent, getting random details and facts is no longer our burden. Instead of using our precious brain power to memorize trivial little facts, it'd be more useful to tightly incorporate critically asking questions while going through the data, noticing patterns and exceptions, and synthesizing more questions or speculations.
Deduce it right there. Sometimes, the audience may not be expecting a perfect answer but rather a "guesstimate." Simply saying like "the GDP is likely low, it's the poorest country in the west hemisphere" can already address part of the question. If you really have no clue, it'd still be great if you can suggest how someone can get that information: "I'm really not sure about that, but I'd look for that in the US Census 2010 Fact Finder online."
While I do notice that you're also asking for advices on how to organize one's research. I don't think I can answer that given how little I know about your work, personality, and affinity to technology. Great research can be done with just a shoebox, index cards, a pencil, and an eraser; it can also be done with a state-of-the-art computer, various software packages, and cloud storage. It's likely something you need to discuss with your supervisors and other experienced researchers, and take and practice what is likely to be useful to you.