There are few things harder than writing something you don't know about. Lets say you've got a brilliant idea for a story involving explorers visiting Antarctica. Assuming you haven't actually been there, I'll bet that it would be challenging for a casual hobby writer to write.
Since I can't suppose how much you know about Antarctica, I'll impose my own knowledge (or lack thereof) for the sake of example.
What do I know about Antarctica, anyway? (Off the top of my head)
• It's cold
• Nothing can live there
• There's an American research station there, which is occupied year-round by only a handful of people.
• Polar bears?
• It's cold
Before long you can see that my understanding breaks down into things I suppose rather than things I know for certain. This is dangerous because it can lead to bad story telling, even for someone who has mastered their prose and can write amazing characters; as long as they're writing something unfamiliar (and unresearched), the story will never be as strong. Think of how embarrassing it would be for a New York Times bestseller to get something obvious and simple wrong, like adding polar bears to a place that has none. It's happened, and it's hilarious as long as it's not yourself.
What I don't know about Antarctica (off the top of my head)
• How to get there (as in, how to charter a plane or boat, who to call, what to say and how long this takes)
• What to bring (I'm assuming at least a parka and a change of undies)
• Who really runs the thing (I don't know if they're volunteers, military or government employees)
• Do penguins and polar bears really live there?
• How cold is it exactly?
• How long is a typical visit to the Antarctic?
• What reason would explorers have to go there?
Apparently the things I don't know outnumber the things I do know. This presents another problem.
At this point I can reassess my situation and make some considerations:
Writing this story seems to be a little bit beyond my current comfort level. I could always research the heck out of Antarctica, but that seems like a lot of work. I think it'll be better if I set the story around, say, a trip to Mount Whitney.
Why Mount Whitney?
Because I've been there. I'll have to do only minimal research, but most of the work is already done. I remember what we ate, what we carried, how we slept (or rather, how we didn't), and how tired I was. There's no effort on my part to fabricate facts or (gasp) research stuff.
This doesn't just apply to locations. Just think of some of your skills and try to apply them to characters. Please don't misunderstand this as an invitation to start throwing self inserts into everything you write. Maybe I should explain some more.
I play piano. Nothing too fancy, but I have an understanding of it, basic though it may be. I know what it feels like to play keys with different amounts of pressure. I know the kinds of weird, abstracty things that go through my head as I'm playing, and I know what it feels like to play for an audience.
This knowledge could be applied to lots of things in a story. Maybe the kinds of things I think about when playing could be used for some kind of computer uplink interface in a sci-fi story, or some brand of magic in fantasy. If you want to go more contemporary and less “out there,” it could be the mind of a crazy person in an asylum. The point is that I don't have to only write stories about people who play piano (which you could also do.) Maybe my story is actually about a mentally insane musical savant whose mind is can interface with an alien computer via musical abstraction. Who knows? I'm really just trying to stay within my level of comfort.
On the other hand, I probably want to steer clear of things I'm unfamiliar with. Like Antarctica, I should avoid things I haven't directly experienced or at least researched to death. Things like:
The death of a close family member
Open heart surgery
“But what if I want to write a story about people riding mechanical steampunk dragons who thwart Nazis via sci-fi mind magic? There's no way to research these things!”
First of all, if that's the story you're writing, I'll be the first in line to read it. Second, you most certainly can research some of that stuff.
If you're gonna be writing about riding animals, you could go find a dude ranch (or a friend who owns horses) and see about riding them. I'm not much for riding, but I've at least done it. If I was going to describe riding a horse, I would use the following phrases:
Jiggling up and down
It's not like anything I've ever done, and for someone who's never stood next to a horse, let alone ridden one, it would be quite an experience (because horses are rather giant).
As for mechanical steam-powered animals, you could probably just make up anything you like. Things that have no frame of reference in the real world are just made for writers to create. The real trick is making these implausible things seem plausible, if not completely possible, and that's what I'm trying to get across.
If you haven't been camping, don't write about camping.