Possibly because I've been working on my latest effort to learn German (I have always sucked at vocabulary, and this newest system must be the best vocabulary builder I have ever encountered), I am thinking about language. I was writing out the description of a creature's shed skin floating in a calm ocean today and thinking, "wow, this is really not the sort of thing you describe ordinarily."
Being able to express an image in words is a core element for DMing, and it takes a great deal of practice. More than that, before you can really describe an image, you must have some sense of what is important about an image ... or more to the point, what is important about being where you can see it.
Take the image below. Describe it for your party, without pulling out an image in showing it to them.
Of course, you can pull out an image, can't you? The internet is there, you can flash up an image and say, "There, that's what you see." For two decades I did not have that option ... and for a time, realizing I could flash up mountains or images of creatures or what have you, I thought, fan-bloody-tastic.
But when the opportunity came to do so, I found there was something wrong. The images did not convey the message. Why?
Well, because the image you pick - such as the one above - tells you nothing about being there. It tells you WHERE you are, but it doesn't answer the question how you are, nor does an image four inches high and six inches wide give you the least impression of the immensity of what's depicted.
There's a very stupid, ignorant cliche that a picture is worth a thousand words. The phrase was obviously invented by someone lacking in imagination, who felt on some level the only purpose of words was to tell you how to get to Bleeker Street (a map is worth a thousand words) or how to recognize leprosy. For such things, yes, pictures are rather superior ... but strangely, where it comes to an artistic expression, it matters which thousand words the gentle reader employs.
IF I want to convey how to recognize an aurora borealis in the sky, the above picture is not bad. If I want to demonstrate that the sky turns color near the horizon when the sun sets, again, not bad. But if I want to express how I know that the sun is setting in this picture and not rising, that's a whole different matter - there's also something weird about the position of the big dipper that suggests this picture has been photoshopped somehow.
In the bigger sense, however, how cold is it? What does this smell like? What can you hear? Are you harried by mosquitoes, does the picture explain the undulation of the aurora, does the picture express the changes in color from this static moment? No. In fact, where it comes to describing the picture for a party, who wants to feel that they are there, the static, dead picture is rather useless. The thousand words you present as the DM are far, far more valuable.
But what thousand words should you choose? As a crutch, I encourage the use of the four senses the picture does not speak to ... particularly odor and sound. Whenever possible, try to attach a good, strong smell to your campaign. And go beyond describing things in a generalized way, such as stinky or musty or sweet. Struggle for those more obscure words, the ones that give a more precise context. The damp, grassy odor of the field after its rained; the uneasy rot of a nearby slough; the dry, powdery dust of the road tickling your nostrils from the horse and cart that has just passed.
Those are not merely lights in the distance, they are the last signs of activity before the darkness settles, and somewhere someone is ringing a bell, bringing their cows in. It's cold, and the first tendrils of the darkness have lifted goosebumps on your forearms, causing you to remember your coat that's been in your pack all day. You remember there's still two more miles to walk to the nearest town, and your stomach rumbles. A meteor glows briefly through the rolling curtain in the sky, and for several minutes, though chilly, you watch the bright yellow fringes grow and reach higher into the sky, coming to dominate not just the edge, but much of the spectacular display. Then, realizing the bright orange has declined to umber, you recall you'd better hurry, you'll be walking in full dark the last ten minutes as it is. Your shoes scuff upon the road, and with habit you tread in the ruts where the stones have been pushed into the clay and its smooth and soft on your feet. You kick a large stone that's been rolled into the rut and remember your jacket again, that you forgot to put on. Not stopping, unslinging your pack, you dig into it, again pausing as you see the borealis is bigger now, it reaches all the way to the east horizon as well as the west ...
It is not only what you see that matters. It is the party's interaction with their environment that you want to convey. Not just the big stuff - there's a huge party, everyone's having fun - but the little stuff too, the fellow pushing his face into the woman's bosom, the three boys scrabbling for a piece of muddy bread that's been dropped on the road, the water with a thin layer of oil in it that nevertheless is just what the party needs right now, they're so thirsty.
It takes practice. It takes standing where you are, and consciously trying to put your world, as you experience it, into words that you can then force others to experience, so that they are in your world. Don't downplay the importance of it. It's not writing, it's performance, and your willingness to practice and expand the texture of your performance will make the largest difference between you as a clumsy, hapless staggering describer of hallways and a brilliant, compelling Dungeon Master.