Creation (of ideas)
Allowing yourself time to just create and capture ideas without forcing them into a story framework allows you to have the craziest ideas. If you're not having to force them you'll find they will grow and develop into pretty amazing things, particularly if you tease and prod them into unexpected areas by asking the simple 'what if?' question. You will know best what stimulates ideas for you – for me it's music – but it's not just the creation of the ideas, it's the capturing of them that's important too. For me a notebook (the analogue kind) is ideal for this – the fact that I'm scribbling away in a book I know no-one will ever read gives me a freedom and security that the cold, hard page of Microsoft Word just doesn't have. The very act of writing these ideas down can also encourage other ideas.
You may have ideas for scenes, characters, emotions, themes or snippets of dialogue or prose – even single phrases. All of them must go in the notebook.
If you've got a good reservoir of ideas building, you'll start to see connections and possible relationships forming between these ideas. This is the next key phase in building a story (or any creative work) – constructing ideas into a cohesive form. You need to have a certain amount of room to experiment in this phase too – this is why so many writers uses index cards, because it provides a flexible way to try out different relationships and sequences. Allowing yourself room to cheaply and quickly try out different connections will also drive new ideas and push the story into interesting new areas. Allow yourself room to experiment here – you're still not committing to anything – you already have your bag of ideas, all your doing here is trying out connections – nothing is undoable. Even the craziest tangential story-thread may yield something you can pull into whatever or wherever your story eventually takes you. You'll find that particular sequences or connections will resonate – and your story will start to form.
If you've done the creation and construction phase then this bit is the fun bit – bringing your creation to life in your chosen medium. This will really be the icing on the cake, bringing all the skeletal elements you've been working on, combining them with voice and style and further nuances – but knowing there's a good solid structure and a strong foundation of ideas to build on.
Any work of any magnitude needs a fertile bed of ideas to grow from. A great piece of advice I once read was 'put every great idea you have into your current work in progress'. A mistake I used to make in my early writing was to have ideas but 'save' them for other projects – with the effect that my WIP was devoid of ideas and appeared sparse and shallow. Don't ration your ideas, use them like a glutton – have faith that you will have more – there's no point worrying about WIP2 if WIP1 is going to be sterile and unimaginative.