The concept is simple.  Look it up before you write it down.  Nothing will stop a reader cold faster than encountering something on the printed page that he or she knows is either not true, or not possible, even within the context of your narrative.  Recently I was reading a sample chapter on a book review site.  The novel was a western set in the mid 1850’s.  The villians rode into town brandishing “44 caliber magnum revolvers”.  Unfortunately for the story’s continuity that style of ammunition would have to wait another hundred years before being developed.  Another example comes from a self-published novel in which the heroine operates an air freight company.  The author apparently did her homework when choosing the  category of aircraft to be used but erred when basing the operation at an airport where the longest runway was several hundred feet shorter than the minimum operating length required for the airplane in question.  For me the story crashed and burned during the first takeoff.  In this era of instant access to information there is no excuse for not getting the facts right.  Admittedly some obscure references will be difficult to find but the accurancy lent to the story is ample reward for the effort.  My Rick Moreno action-adventure series, beginning with The Case of the Very Hot Car, is set in the mid to late 1980’s.  Some of my research involved a seemingly simple task, finding hotels in various towns that were in business during that time frame.  It proved to be far more difficult than I would have expected.  My western, The Time of the Preacher, spanned the years from 1853 to 1901.  Weapons, transportation, the emergence of rail travel, the growth of towns and cities, in fact all the aspects of life during that time had to be checked for accuracy in order to build a believeable backdrop for the characters as they moved about their daily activities.  In summation, before you offer your prospective best seller to the public make sure that you haven’t sent Sitting Bull up against the Seventh Cavalry armed with an M-1 carbine.