When preparing for presentations, I comb through the web and alot of books. When possible, I hit the national archives for records and in some cases, records from the manufacturer. The key to presenting useful information is to never take anything from a single source, no matter how good it appears. I have seen wide ranges of things, like surviving examples is a good variance. In those cases, I usually state that exact numbers are not known, but the estimates are between x and y.
I also have a great aviation library at my disposal at the museum, plus guys that flew and work/worked on the aircraft during and after the war. I always verify verbal facts though, because in some cases, you are hearing a memory from 60 years ago.
I am not an expert either, I learn as I go through each presentation. Whenever possible, I try to get someone who was involved with the aircraft to speak. One of my best guests was Don, who flew in the battles of Midway and Leyte Gulf. He is normally a quiet, unassuming man. Once he got talking though, it was truly amazing! He is also well organized and has folders from the different battles he flew in with pictures and unit histories. His records are a historians dream!