Came across a question about research, posed in the blog of Medwayscott (follow the link and read his post before continuing, that might be best).
Anyway, he said some very nice things about Salvation's Reach, the most recent Gaunt book, and was very complimentary about the Navy action depicted in it. How much was researched, he wondered.
I do a LOT of research, for pretty much everything I write, which may sound faintly bonkers considering that what I write is Made Up Stuff. My contention, and I've stuck to it for over twenty years, is that SF and Fantasy work best when they feel authentic, when they seem grounded and real. So my basic approach is to consider each book as if it were a 'real world' or even historical novel. I find the closest thing in the real world to the fantastical thing I'm writing about, and research that, then convert laterally into the fantasy frame. So... writing about Kislevite Lancers (as I did in Riders of the Dead)? NO such thing in the real world, obviously, but how about 17th Century Polish Hussars? Let's go! 40K air combat (Double Eagle)? Let's try the Battle of Britain and mix in a little Korean War and modern theatre jet warfare. TItans... and, indeed, Imperial Navy vessels and engagements (various, but especially Titanicus and Salvation's Reach)? Let's look at the British Navy, let's look at U boats and other submarine experiences. Let's visit Chatham Dockyard... ;)
Right now, I'm writing about court intrigue during the Horus Heresy, so I'm ransacking all the stuff I can find on the Tudor Court, the Vatican, Italian Principalities, Imperial Rome etc. etc.
But when the (goodness me!) half dozen Primarchs I'm handling here start duking it out through a city hand-to-hand, I don't know WHAT I'm going to start looking at. That may be when fiction starts looking at other fiction, and I start drawing on the thousands of superhero comics I've written over the last two decades...