One obstacle to writing is description.
Yes, I said obstacle.
The problem with description is that many people, heady with the rush of a clever idea, or in a hurry to get the story written, use description totally incorrectly. They can be very good descriptions, but they're still the wrong descriptions.
How can this be?
Here's some old descriptions I wrote years ago, from my description-mania period. (Description-mania is a symptom of writers who create Mary Sues and the like, by the way, and the types of descriptions we see of Mary Sues are maniacal descriptions. Fanfic writers take note.) They're three monstrous descriptions of various creatures.
This creature stood on the spindly, jointed legs of a sea spider, with a body like a manta ray’s. There were several poisonous spines on his tail. Two “horns” projected from his head next to the eyes. Surrounding where the mouth would be were eight spiny tentacles, and instead of a mouth inside the ring, there was a long, trunklike proboscis. Mounted at the end of the proboscis there was the head of a hammerhead shark, warily watching the others as its jaws worked convulsively.
An armored body with large, sensitive eyes that were surprisingly well protected narrowed into a long tail tipped by a combination stinger, acid sprayer, and spinneret. Long, spindly legs proved surprisingly strong, supporting the monster and whisking it along the ice and snow at amazing speeds. Powerful jaws surrounded by menacing spiked limbs snapped in anticipation. Enormous pincers extended forward, ready to crush [some guy]. The whole creature was the size of a main battle tank and twice as heavy.
Massive jaws clattered convulsively beneath gigantic, domed eyes that glistened in the light. Mighty wings beat the air ferociously. The creature’s body was well-protected, and a tail tipped by a pincer-stinger whipped about. The limbs were powerful and clawed, and extended forward, searching for something to impale.
Ha ha, get it? They're descriptions of monsters? They're-Never mind. These things hijacked entire paragraphs. The second two occured within two paragraphs or so of each other, which made them even worse. They sprawled across their pages. They demanded attention, and slowed down the reading. If you want the typical modern audience, who prefers their books fast-paced because they watch movies and television, this descriptive style is too clunky. If you can make this deliberately funny (Terry Pratchett and Douglas Adams both put this in a lot of stories, IIRC), the reader will probably not be bothered so much.
Here's something from just a few years ago, when I took a creative writing class.
It was like an insect, with an articulated shell, but it had only four limbs in all, and if it was in a lifelike pose, it had stood on its hind legs in life.
This is getting in and out of what could have been a quite complex description in a hurry. It establishes a fact on the subject's appearance (it's like an insect), which will immediately give the reader a lot to go on. Then, it mentions how to differentiate it (it stood on hind legs, and had four limbs instead of six). It's still detailed enough that many will have a picture in their heads (although most will have a somewhat different one, one of the few flaws of the method).
Generally, this level of description can be quite effective, if you slip bits of it in between actual story bits, or mixed in with the story's actual action ("the monster, now full-grown, blah blah fishcakes ate people").
Then there's this level of description.
Mary was hot.
The key, of course, is striking up a balance for one's own story. The preceding description lacks elaboration-was Mary hot because the air conditioning had gone out? Or was she hot because she is very good looking? Or has she spontaneously combusted?
Not good description either, unless you're being funny again, and possibly using the ambiguity of the description. (Maybe Mary is a pyrokinetic? Or even just a pyromaniac?)
The key, as always, is to match the style of description to your story and even your audience. My sister remarks that little kids love long descriptions (this may be why fanfic writers tend towards them, for one, as a lot of fanfic writers are pretty young). Older writers tend to cut out a lot of the story flab, and apparently older readers don't mind this. (It depends on the oldster, I suppose.) And there's no end of variation inbetween.