So you've got your main idea, a character and a place to explore. Awesome! Now you need detail.

Of course, this is the part that I can help least with- this is where your imagination can soar, and there's no telling what adventures your story will take you on. You are the mastermind, the director, the creator of this world, and you have the power to make it come alive, whether it be a pure world of fantasy or a throwback to past times. However, to give your story real depth and a firm grounding in reality, a basic knowledge of eras gone by is increasingly important.

The culture and every day life of the world you create is a vital part of the mechanics of your story. Society involves politics, economics, and ethics. Society is usually at the heart of a thrilling read, whether it be about a character rebelling against it's government or ideology, or a wider sceme; it's important to remember that it is people who make up a society (but by now, is it the society which makes the people? Ooh philosophy)

A good political system to impliment in your imagined historical kingdom is the Feudal system. Many places have feudal histories to draw upon- England and Japan being two fascinating ones. Of course, medieval fantasy does not have to be exclusively based on this, and if you're particularly interested in regimes and politics you can do what you like and see what kind of a government evolves in your own world.

When it comes to technology, remember what had and hadn't been invented for the general era you've picked. If you're not sure whether something's been invented yet, consult google. I've discovered many-a interesting thing while researching, such as a brief history of bricks and how glass was cut back in the day- even how to home-make a reed wick if the family's too poor to afford candles or oil. You'll be full of general knowledge through the endless research writing brings.

If you want to go further back than medieval, celtic or old english history might be the way for you. Or Nordic. Or Ancient rome, or Greece. It depends on the kind of feel you want in your story; even the climate of your world could influence the cultural background you want to draw upon.

Of course, a huge part of any culture is the folk lore and traditions. This is really a place with vast, easily limitless room for big ideas and tremendous imagination. Let loose, open the floodgates- this is a fabulous part of your world, and absolutely a joy to create. Are there any secret societies? Legends, warriors who went down in history? Prophesy, rituals?

Also, while you were picking out the setting, I'm sure you have some kind of landscape mapped out in your head- but why not take it further and browse galleries on an image site? Find interesting local wildlife that could live there or plants which only grow in that climate. Or just make up your own. Think of standard building structures and special landmarks.

It is also important not to forget that many places were highly religious, and it's worth incorporating a faith or spirituality into your world. If you're not religious, of course it's not compulsory- but if you want to critisize the grip religion had/has over society back in the day or even now, well, there's a chance here; and if you want to show what a religion can do for the people, showcase it in the world you've created.

A great website called all things medieval is fabulous to browse if you're not sure what you're looking for but want to know more.