Every scene that you write doesn't necessarily belong in the finished draft. A lot of things you may have written just to keep writing, or they were scenes you needed to know about but your readers don't. Part of writing a first draft is learning about your characters and figuring out the story. So some of your initial writing may be you playing around, testing the waters. So how can you recognize the fluff from the important scenes?
An awesome trick I learned several years ago comes from screenwriting. Get a pack of index cards. Go through your novel or short story and write down a scene per index card. Number the scene, and in a sentence say who is in the scene and what they're doing. Once you're done, lay out the index cards and read your novel in summary. You will immediately recognize the cotton candy from the steak because the one-sentence summary will read something like "Rex and Sir Edmund chat" (from an actual scene card of an old story of mine). Laugh if you want, but I promise somewhere in your novel or short story is a scene like that and this method will smoke it out.
How do you cull out the filler from your stories?