I've developed a 'trick' to help myself with this problem. It's nothing complicated and is extremely simple, if not overtly obvious, but I've found it does help me. After I've finished writing a scene, I'll do a re-read with a piece of scrap paper handy. As I'm reading, I sketch out the scene that the page paints, drawing only what the words describe. I'm not talking about an artistic sketch--just stick figures and basic shapes will do. This little diagram visually illustrates to me what I've described for the reader. And if the picture is incomplete, I know where to add written detail.
Here's a quick example, using the paragraph below:
I would have the following sketch (please, control your laughter--it's for illustration purposes only!):“Hate unnaturals,” Yduk Thiern murmured. “Always have, always will.” He stroked a hairy mole on his chin, while his boot sole slid back and forth across the desiccated surface of a coney skull rotting in the brushwood.The bashful breeze ruffled not a hair on Yduk’s eggshell-bald head. His greasy moustache hung too heavy to be bothered by a timid zephyr. Clad in burnished black-lacquered buckskin, he wore a hand-and-a-half sword on his hip and a crossbow over his shoulder. Dwarfed by the larger weapons, a deadly-thin dagger also hung at his belt. He stood unmoving—tall, lean, and hard—blending with the shadows.Now, past midnight on a cool summer’s eve in the low foothills south of Dwim-Halloe, he waited beneath an ancient Elven tree-tower. An unnatural lived inside.In the oak forest sprinkled with whitebeam and wych elm, a giant ash loomed overhead, silvery bark magnificent in the moonlight. Long ago, the elves constructed a slender dwelling wound around the trunk, high in the concealing branches.Now the elves were gone, and a fugitive mage resided in the woodland spire. The Southlander intended to collect his bounty.The tracker scrutinized the rangy tree. With no ladder or low branches, he wondered how he would ascend to the elevated entrance of the unnatural’s dwelling.
The sketch above is the imagery you can expect your readers to 'see' if they catch all of your descriptive text. If this doesn't match the movie in your head, or something important is not shown, now is the time to fix it.