Breathe some personality into your characters. Give them each a set of flaws, quirks and internal conflicts, leaving them room to mature throughout the narrative. Jot down the history of your main character; include family issues, insecurities, pet peeves and interests. Even if you don't reveal this information during the course of the story, having intimate knowledge of your characters can help you envision them.
Write about places you've visited or researched. If you base your story in ancient Rome, you'll need some knowledge of the architecture; otherwise, your setting will feel flat, like a cardboard background. Of course, if you're writing a fictional story, you can create a fantastical setting. Whether the setting is realistic or fantastic, give it an atmosphere. Describe its climate and landscape. Give a brief description of the population. Are the inhabitants cheerful folk or downtrodden cynics?
Some writers prefer to outline the events of the story before beginning. Other writers would rather let the plot flow whimsically. There's no right or wrong way to go about it. However, if you're prone to writer's block, consider at least developing a loose outline. Don't be afraid to deviate from your set path if the opportunities arise.
When choosing your storytelling perspective, consider your characters. A first person point of view allows for a more intimate and emotional view of your cast. The various degrees of the third person perspective can pull the reader further away from the inner workings of the characters while presenting a wider scope of your world. During the revision process, explore your other options. You may discover that a different perspective works better than your original choice.
When depicting images, some writers prefer to give long, detailed descriptions. Other writers like short, clean descriptions or even staccato images comprised of sentence fragments. No matter what your style, avoid clichés when producing imagery. Opt for creative descriptions and imaginative similes.