Before you start writing your story, get a clear idea of your central characters, location and dramatic predicament.

The Three P’s

All you need to start writing your story are the Three P’s: Once you’ve got those basic elements you’re away, and can start writing your story. But it may take a little thinking before you get the Three P’s clear in your mind.
Different writers get them in a different sequence; and sometimes the sequence varies from one story to another. I’ll describe them in the order place–people–predicament, simply because that’s a convenient way to describe them here.

Place

The first P — place — is more than just a location on a map; it’s a whole atmosphere of the story. For example, Colin Dexter’s Inspector Morse novels (and the TV series based on them) take place not simply in the town of Oxford, but in the whole scholarly world in and around Oxford University. This creates an atmosphere of quiet academic enquiry, and also begins to suggest stories. Morse is inevitably drawn into mysteries of intrigue among the educated and affluent. The murders are crude and violent, played out in a world of seething academic jealousies and long-suppressed family betrayals.
A different TV programme, Buffy, has its own distinctive location. Again it’s not the town but the places within the town: the graveyards, gothic crypts, and shelves of antique books. The ‘place’ is a world of night-time shadows, where threatening graveyards mingle with basement nightclubs. Much of the programme inevitably takes place in daylight, but just watch the opening titles to see how much it depends on dark shadows.
So location is not just a place on a map; it’s the whole landscape and environment. It’s the architecture, the social relationships, even the climate. When you’ve got the location for your story, you’ve got the complete atmosphere, and maybe also ideas for characters.
In case you still think place is unimportant, it’s worth noting the recent words of crime novelist P D James:
Setting, important in any work of fiction, is particularly so in a detective story. It establishes atmosphere, influences plot and character and enhances the horror of the murder. For me the novel invariably begins with the setting. (Guardian Review, 6 March 2004)
Like P D James, you may find that place is the first significant choice that comes to you when developing a story, and which then guides the whole of the subsequent story.
Your locations may come from places you know, or have visited, or maybe just passed through. They may even be places you’ve only seen in pictures. I once got ideas for a story from a nineteenth-century photo of a misty coastline, and a postcard reproduction of bombs piled high in a Second World War munitions factory.
You may even find locations in other works of fiction. Writers often get ideas from other stories. It’s the Magic ‘What If...’: you see something — in your everyday life or in another story — and you suddenly have an idea for a completely different way of using it.

People

The second P is the people in your story.
You probably only need two people to begin your story: the two characters whose relationship dominates the story. If it’s a story about conflict, then you need the two characters in conflict. If it’s a story of love, then you need the two characters in love. If you’re writing about a love triangle, you may need three characters — but look at them carefully, because you’ll probably find that two of them are more central to the story than the third.
Be very careful about kidding yourself that you ‘need’ extra characters to tell your story. You don’t. Naturally you’ll create more characters as the story progresses, but you don’t need them to begin with. In fact extra characters are a distraction, so concentrate on your two leading players.
If you’re having difficulty focusing on only two leading players, apply this test to each of your characters in turn:
If I took this character out, would the story still happen?
All significant characters have an effect on the story; but most of them only affect how the story unfolds. The two leading players decide whether the story happens at all. If you take them out, the story doesn’t even begin. For example, the action of Ibsen's play A Doll's House couldn't begin if either Nora or Helmer were taken out. If the blackmailer Krogstad were taken out, it would be fairly easy to create alternative ways of revealing Nora's secret. But the central story turns on the secret which Nora keeps from her husband, so the story needs those two central characters in order to take place.
One of your two leading players will be the single ‘Leading Player’, but it’s not always necessary to decide who right at the start. It may be possible to begin writing the rough draft and see which one emerges as the central player. A useful guide is to think
Who takes on the problem?
A story shows us how the Leading Player takes on and resolves the story's central problem.
This test helps locate the focus when you’ve got two central characters who seem ‘equally matched’, such as two lovers in a romantic comedy. Think about which one does most to take on and resolve the central problem. For example, in Nora Ephron’s movie You’ve Got Mail, Kathleen and Joe take equal initiative in the love affair, but Kathleen is shown as more active in the conflict between the large bookstore and the small corner bookshop.
Once you know the two essential characters who make the story happen, and which of these is the Leading Player, then you know who the people of your story are.

Predicament

The final P is the predicament. Your story must begin with some kind of dramatic ‘situation’: a problem that needs resolving. There’s some kind of misalignment, imbalance or distortion in the opening state. Maybe a murder has been committed, or a secret intrigue is taking place, or a character is about to marry an unsuitable partner, or a tyrant is in control. This is the opening imbalance which must be put right.
The predicament might be a plot predicament or a relationship predicament. In a plot predicament there’s a problem with the general situation: a crime that needs solving, or a Bad Guy terrorising the neighbourhood. In a relationship predicament, there’s a problem with the central relationship: the two lovers are engaged to marry other people, or two cops are struggling with the deep antagonism between them.
This basic predicament exists right at the start of your story. The characters may not discover it until later. Some crucial event, such as a murder, may not yet have occurred. But the underlying ‘dramatic situation’ exists right at the start, and this provides your story with its opening predicament.

Make It Extraordinary

Finally there must be something unexpected in your Three P’s, to catch the audience’s interest. A story about two ordinary people leading ordinary lives in an ordinary town has absolutely no appeal at all.
Good stories are about either ordinary people in extraordinary situations, or extraordinary people in ordinary situations. Either way there’s something unexpected. Audiences like to be taken to new places and introduced to unusual people.
You can develop your Three P’s in any order. You might start with a couple of great characters, and then think about what happens to them. Or you might discover an evocative location, and start wondering about stories that might take place there. Or you could begin with an idea for an interesting situation, and then think about the characters who get involved. You choose.
Once you’ve got the people, the place and the predicament, taking us somewhere unexpected, you’re ready to tell your story.