I recently read and critiqued a first-draft of a story and I wanted to share some advice I gave for the next draft. I'll summarize and generalize, and hopefully somebody will find this useful.
1. Remove any word that does not contribute to propelling the plot forward.
You've probably heard this before--because it's sound advice. Too many irrelevant words can lose a reader--especially now a-days, when people are used to reading short Facebook and Twitter posts (did you know that many people are losing the ability to "deep read" text (do a search on digital reading)? Keep reading novels, people).
If you need practice with this principle, go stick a few of your sentences into Twitter posts; a character limit forces you to become creative and often makes your sentences more interesting.
2. Be sure to characterize.
I want to feel a connection to a character--especially the main one. I want to know why a character is the way they are; what events made them that way? You don't have to tell this--I do not want to hear that they are the best detective in the city because they've solved 1000 criminal cases, or their accuracy with a gun is akin to a god's. That sounds like a lot of hot air if there's no evidence to support it. Show me why they're (allegedly) the best.
It's also irritating if they seem infallible. If a character has no way to be defeated, there's no point to the plot. People have to win some and lose some. Now, don't fall into the pit of your character is too weak--a character who loses over and over again is also irritating (unless they're a side character and it's obviously for comedic effect); often times, this leads to angsting, and I don't want to read an entire book about angst (unless it's really good and the plot is compelling--see Monsters of Men).
I want characters with emotion who move the plot forward. Give them personality and a back story, then slowly give it to the reader.
3. Balance between slow and fast.
This one is a hard one to explain, and probably harder to follow, but basically it goes like this: rushing around all the time can get confusing and overwhelming for a reader. Having one action scene after the next can get exhausting. Readers need to breathe a little. Unless you're at the BIG climax, action scenes should be tastefully spread between scenes that build up to action scenes. We need to know the reason behind stuff and what's going on. Build up suspense with the slow stuff.
However, be careful with slow stuff. In the latest Green Rider book, the fifth one, (which I hate) it takes like 15% of the book to get anywhere mildly interesting--because the main character is bed-bound, and she's not even snooping about.
Slow stuff doesn't have to be boring. Make the contributions to the plot be interesting, and it won't be boring.
I hope that section makes sense.
4. Read your writing out loud.
Not only can you more easily find grammar and spelling mistakes this way, but you'll probably find yourself stumbling over some words because they don't flow. A lot of people don't have a very well-developed internal-voice, so they don't "hear" the words in their heads.
Reading it out loud forces your brain to look at each word--reading in one's head can filter out certain words. Did you know that if you have two 'the's right in a row, the brain usually skips right over it? This is why the the act of reading it out loud helps. Did you see what I did there? If you didn't, read that sentence over again, verrry slowly.
5. Get an editor.
If you're on the last draft, and you're planning on self-publishing whatever you're writing, please, please, get an editor (as well as some beta-readers and proof-readers). A second set of eyes always helps. Don't finish your NaNoWriMo novel then instantly put it on the market. Bad, bad idea. There's nothing I despise more than picking up a book and finding two or three errors in every other sentence.
Do your editor a favor and don't send the first draft into them, however. Get beta-readers early on and do a few rewrites, then edit it yourself the best you can. This will save them a lot of headache, and it will likely make your story better. If your editor is less focused on grammar and spelling mistakes, and you've done your bit to try and clean up the plot, then they can help more towards content.
7. Always write, read, and review--often.
The only true way to get better at something is to do it over. Again, and again. Save your writing, and look at it two years after you've written it--you might be amazed at how far you've come.
Read other people's stuff! I'd advise reading mostly good writing, but sometimes it's useful to look at what not to do (see the fifth book of Green Rider).
Review other people's stuff! When you dissect someone else's piece, it often draws attention to what you've been doing wrong in your own writing, and you can make notes what not to do, or what to do better, or what things you like.
Welp, I think that's all for now. Go crazy with Google if you want some more revising tips; tons of published authors like to tell people how to write (and, seeing as they're published, they must be doing something right, so they're probably worth listening to).