When creating a story, we tend to think of it as a sort of overwhelming whole rather than small little chunks that make up that whole. By approaching and tackling your story a scene at a time, you'll soon find that you will have it finished in no time. Here's a list of what to think about when writing a scene and how to write it.
What sort of scene are you writing? Fighting? Romantic?
Quickly figuring this out allows you to create the scene like a 'mini' story as it were, and research what needs to be included in it.
Which of your characters are in the scene?
If it's your protagonist, are there any secondary characters too? Do they help or hinder the scene?
What is the main goal of the scene?
Approach it like a mini version of a story - how does the scene start, what happens during it, how does it end? Is the goal a failure or an achievement?
Where does your scene happen?
Figuring this out will allow you to create some good descriptions that sets the scene for you.
How long is the scene?
Will it happen over several pages, allowing you to expand on description? Or will it be short and mainly dialogue?
Is there an alternative way you can start the scene?
Try several ways of doing this. You may find one way works better than another.
Can this scene be cut?
Finally, after writing your scene, be honest with yourself. Does it advance your story in any way, or can it be cut? Each scene should do this, and shouldn't just be a 'filler' to pad out your story.