First, let me say that I am sorry I did not have a review up on Friday. I was on vacation and did not have time to read anything. Also, this writing tip (while usually on Wed.) is today because I will have a tour post on Wed. Come back for that, it will be awesome!
So, research. It is so very important. Some people might think it is not needed, that you can just write about things you don't know, and no one will notice. I tell you, they will.
Here are some examples in books I have read where it was obvious that the author had not researched things.
Chosen by Ginger Garrett: Now, I love this author. She writes some amazing stories, but it this novel she messed up. In this novel about Esther, the heroine eats a dish containing tomatoes. Now, you might wonder how that is wrong, but no history buff does.
Tomatoes are native to the Americas and did not show up in the Old World until after Columbus, meaning that Esther could never have eaten tomatoes. It turned off a lot of people to ever read anymore of Garrett's books that she got something like that wrong, as can be seen by reading the reviews of it.
Forevermore by Cathy Marie Hake: In this novel, Hake mentions Cinderella. A character reads the tale to a child and mentions the mice in the story. As a historical, this is wrong. Disney's version is the only one with mice in it (that I know of) and so they never should have been mentioned because they would not have been in the story at that time.
So, even if you think you know something, research it. Research foods and clothes and names. Anything and most everything. Believe me, it is hard and often annoying (I wrote a whole story once, only to then learn my hero's name was really a last name). You just have to press through and remember that readers will notice if you don't take the time to research.