Perhaps it’s a carryover from my article writing days, but research is an integral part of my writing process along with plotting, writing, and revising.
The reason for research is simple: to bring an air of authenticity to the story. Even a science fiction writer is likely to consider the laws of physics when creating an alien world. Authors whose stories take place in different times study the customs, language, settings, etc. The Prohibition world of 1920s Chicago is far different from today’s Windy City.
I’ve been engaged in fact-finding since high school. Even then my stories were set in the past (usually Prohibition). Plots take place during the French Revolution, Colonial America, and World War 2. Recently, I’ve started exploring the Victorian era but haven’t yet found myself brave enough to attempt steampunk. (More research is needed.) :-)
One of the biggest benefits of research is it can lead to interest in other areas. The problem is I can become so absorbed in the new information, I forget my original idea. (Which is why I write them down for future reference.)
Research can also be a starting point. For example, in Death Sword, Xariel, an angel of death, suffers from a sex curse as a result of his teaching the lunar cycle and his former relationship with Samael. During my studies of angels, Xariel (Sariel), also a Grigori, taught the lunar cycle, which apparently was forbidden knowledge. Whether or not he was actually punished for this action, or for simply joining the other Watcher Angels, is probably debatable. For me, the important thing is how this punishment affects his character as well as his motivation(s).
Is research necessary? Depends on the author’s preference. Me? I’m the type of writer to go so far as to find out the temperature of a certain location. For example, in a short story I’m writing, I need to know how cold it was during the Louisville winter of December 1917. This way, I know what my characters will wear and how they’ll react.
Apparently, it was pretty damn cold.