Writing historical novels

It is easy to become carried away with the allure of lovely clothes, and stories of an age when men were men and women were - well, women. However, there is much more to writing a historical novel than that.
It is what is says - history. Not fantasy, not fairy stories, but history. I believe that we owe those people who lived in those times us a measure of respect by getting it right, or as right as we can. Here are some hints on how to do it. This is not a 'how to write' guide, but with the historical novel specifically in mind, it's an attempt to show how to imbue your book with the real spirit of the age.
In order to know how people thought then you need to know the politics and economics of the age. This is the backbone, the structure on which everything else is laid. The best of these are obtained from the kind of textbooks you probably remember from school, and it has to be done. Read more than one, and don't believe everything you read - historians have a point of view, too. The facts are there to read, but the importance of them is relative to whatever argument the historian wants to put forth. Therefore it is necessary to look at the types of data available:

Primary data is contemporary data. Depending on the period you wish to explore, it includes newspapers, letters, essays, and novels of the time. It also includes actual items, like furniture, costume and buildings. Do not assume that the only primary data is written. Before the advent of printing, there were other forms of literacy. The average medieval peasant could 'read' a painting much as we read books. Meanings that are hidden to us were clear then, such as the colour a character was dressed in, their posture, even their position in the geometry of the painting.

Secondary data is usually written, and is written after the event. So a Victorian's opinion of the Georgian age may actually say more about the Victorians than the Georgians. There is a lot of this, and it needs sifting through carefully. There are so called 'histories' that are wildly inaccurate, for instance. Ask other people what they think of the work, and always, always double check. Look for other sources, other books.
As well as the history of the age, it is important to understand the zeitgeist, the spirit of the age. Morals, manners, opinions, why the people who lived then behaved as they did. Since this is rarely a matter of fact, heated discussions occur more about this than about the actual history of the time. Immerse yourself in the history of the period. Visit the places you want to write about.

Sources of data. In the old days we just had the local library, and what we could order through it, together with the museums and galleries we could physically visit. Now we have the Internet. You can take virtual tours of great houses and museums, find primary sources previously only available to the dedicated scholar. You can download e-texts of out of copyright books for free. However, with this we also have highly inaccurate sites, perpetuating myths and deliberately distorting history for another, not always obvious, end. Try to discriminate. Never depend on one site alone for information. Always check it, as much as you can.

Lots of work, but if you're clear about writing historical novels, it should be a pleasure rather than a chore. To write successfully about an age you need to understand it.

To finish, here is a list of common mistakes I see over and over again in historical novels. Note I'm not talking about writing craft, such as pacing and grammar, but specifically referring to the historical aspect.

1. Mistakes with titles. Once you understand that an aristocratic title belongs to the Crown and is only held by the duke, earl, etc, things become a bit clearer. In fiction, I've seen illegitimate children inherit, a duke decide which of his children can inherit, a girl inherit over a male heir, a peer 'disown' his title to sit in Parliament (possible now, but not before around 1960), and terrible mistakes in address. A duke is not usually called 'my lord,' nor is the daughter of a baron entitled to call herself 'my lady.' Only in fiction. None of these things can happen in real life, because the people of the time were brought up to know these things.

2. Anachronisms. Kilts and clan tartans in the twelfth century, a camera in Regency England. A character who says, "get with it," or something else that screams twenty-first century slang. Many readers of historical romance know a great deal about the period, and very few things are guaranteed to drag a reader kicking and screaming out of a book than getting it wrong.

3. Language. The most common is Americanisms in books written about British characters. British people do not say "gotten" or "visit with." They do not wear vests on top of their shirts, and suspenders aren't used to hold up trousers. If an author uses her own voice to describe things, then this is completely acceptable. However, in a book where the main voice is the third person limited, it is completely wrong. You have to think as your characters think, and that includes using appropriate language.

4. Scottish castles. Most of these were built in the Victorian age, and a lot of what we consider "Scottish" like kilts and tartans, are actually Victorian. In the sixteenth century Scotland was a highly civilised country, as it was in the ninth. Castles were built in the Fontainebleu style, to be more decoration than fortification.

5. Geography. There are contemporary maps that show the difficulties of travelling in the age before the aeroplane and modern roads. Make sure you know the country you are writing about, not some other person's opinion of it.

All this, on top of the other lessons you can learn about writing! Who needs it? If you want to write a book about characters who lived and breathed in the age you chose, you do. If you want to make a quick buck writing a book with people in fancy clothes who have lots of sex, then you don't. You don't have to be historically accurate to get your book published, so it's up to you.

Finally, don't be afraid of making mistakes. Even the Queen of the Regency genre, Georgette Heyer, made the odd mistake. Just try to minimise them, don't make the same mistake twice, and do your best.
Now get writing!