Oh, this topic sounds terribly exciting, doesn't it? No? Well, hang with me anyway.
I recently wrote a picture book with sailors and pirate characters. As I wrote my draft, I did a little online research for some of the sailing terms and such. Found some cool sites, like the Talk Like a Pirate Day site and this pirate glossary. They were both helpful, but even more helpful was a night of sitting on the couch watching Pirates of the Caribbean! More than reading about the lingo, I really needed to hear pirates talk. The movie made that possible for me.
A lot of my "research" is done just by being observant of ordinary things and people. Not long ago, Corey and I were working on a story written with the voice of a 6-year-old boy. One line we considered was, "My tent had a big, huge rip." Should we use that line, even though it's not very poetic? I got my answer a few days later as I was working with a kindergarten boy and the words "big, huge" escaped his lips! AHA! Kids really do say that still.
That's not to say that line might not change eventually. But the point is, a lot of my (and your) research can be done by simply being aware of what's going on around you. For me, watching and listening as kids interact with each other is a valuable part of the writing process.