While this will indeed be a case of the blind leading the blind, I like to think of it more as the blind leading the blind-er. This is not meant as an insult or an implication that I'm better, but I have noticed a few things through a lot of people's fics, especially new writers, that are signs of amateurish writing.
Of course I've made these mistakes myself, but I've also had them pointed out to me, sometimes in not so nice ways (beware of the evil Creative Writing Teacher's Assistants). I thought I might try to spare somebody the same bitterness and hatred I've felt. Thought I was going to say pain and humiliation? Trust me, when someone criticizes your work, you can either be hurt or be angry. Angry is better, since you can cool down and see if they were right or not. Hurt means you're not getting better.
Writing Tip #1: -ly, -ly, -ly
Don't use a lot of adverbs. Use them only sparingly. If you want to show that someone says something angrily, don't say it. Show it.
Example:
"No," she said angrily.
"No," she said, stomping her foot.
It took me a long time to figure out the difference between telling vs. showing, mainly because my idiot highschool teachers never explained it, but my college teachers did.
Writing Tip #2: said, intoned, dictated, stated, asserted...
Use said. Always use said. If there is a rule in Creative Writing, that is use said. I know you're a writer and know a great many words to use instead, and I know it seems repetitive to say "he said, she said" all the time.
Do it anyway.
Don't believe me? Pull a book down from your shelf. Any book. When you do see dialogue, what are the tag lines (that's the fancy term for he said, she said, they said) that the author uses? Only rarely do they use something else.
Plus, I'll let you in on a secret. When you read a story with dialogue, and the only tag is "said," you'll start to tune out the said's so that they're only good for telling you who's speaking. That's good.
An exception to this rule (because there are no rules in Creative Writing) is when you want to emphasize something.
Example:
"I don't get it," he said.
The tag line whispered emphasizes that last line and packed a lot more into the words that if we tried:
"I don't get it!" he yelled.
Last note: Asked is also okay. If you really have to, yelled can also be used, but generally it's better to show their feelings than say it. Plus, when the tag line tells the reader how the character said something, it might be different than how the reader took it the first time. Let the reader's interpretation stand.
Writing Tip #3: !!!!
Don't worry about exclamation marks. You notice in the previous example, I could have put an exclamation mark with "No," but I didn't. The statement didn't need it.
Example:
"Luke," Beru called over the sands. "Time to come in!"
"Very well," Darth Vader said. "If you will not turn to the dark side, then perhaps she will."
The differrence? Even if someone's raising their voice, it doesn't need exclamation points. Beru may be screaming her lungs out in this version when she's really only raised her voice a bit. Indicate their voice is louder either with a tag line like "called" or a motion, like cupping her hands over her mouth.
Also, if you've watched Return of the Jedi (and who hasn't) you know that scene in the movie is the turning point and a rather emotional scene. Plus, Luke was yelling at the top of his lungs. Top-of-the-lungs yelling is the only time you use an exclamation point.
Writing Tip #4: Grammar Strangleholds
You remember your good grammar rules, right? Don't start a sentence with a conjunction like And, don't end a sentence on a preposition like out, in, over, etc, don't use slang like ain't, and don't use contractions like don't.
FUCK GRAMMAR. WRITE CREATIVELY.
Stop cheering. That said, you still need to use good grammar mostly in the name of clarity. Good syntax and noun/verb agreement is vital. If your writing totally confuses your reader, that's not good. You're not Faulkner yet. When you're nationally recognized, then you can go nuts. Until then, you have to write right.
ONLY dismiss grammar when it either 1) confuses what you're writing, or 2) it hinders what you're trying to write.
One word "sentences" are okay once in awhile, like a commentary from the narrator.
Example:
He whirled around and around, trying to find the source of his brother's laughter, but his brother pushed him from behind into the mud. He fell into the mud, and his brother pressed a boot into his back from behind. He felt pathetic.
He whirled round and round, trying to find the source of his brother's laughter, only to be pushed from behind. He fell into the mud, feeling a boot on his back press him down. Pathetic.
The top one is grammatically correct, but it is as coherent as the second? The second one is better for a couple reasons. It focuses entirely on the guy doing the whirling, so the pronouns don't get confused. And the ending "Pathetic," seems to be part of the narrative but actually is what the guy in the mud feels about himself, OR what the brother feels about the guy in the mud. It also lends emphasis to the feeling of derision. It's all these things. Much better than the first, hm?
Writing Tip #5: He, She, They, We, It
Tying in with tip four, about pronouns. Try to keep them clear. It's easy enough if you have a guy and a girl talking, since you can keep to the "he said, she said" and not worry about people getting confused, unless they're REALLY open minded. Get two guys or two girls, and things get a little more difficult.
One thing to do is just add more narrative to your dialogues. You can also use people's names in the tags, especially when your dialogues get long. No example on this one. It'd get way too long.
Writing Tip #6: Paragraph breaks
Break your story up into paragraphs. I know this sounds like a no-brainer, but there's folks what don't do it.
More to come as my ego inflates...
 
"I'm not going to tell you again," she said.
"But can't we just--"
"No. No, we can't. That's what I'm trying to tell you."
"I'm not gonna buy that. Why? Why are you leaving?" he asked.
"I can't tell you that," she whispered.
"I'm not going to tell you again!" she screeched.
"But can't we just--" he sniffled.
"No. No, we can't. That's what I'm trying to tell you," she stated.
"I'm not gonna buy that. Why? Why are you leaving?" he asked angrily.
"I can't tell you that," she whispered.
Luke came out from behind the pillars, lightsaber blazing. "Darth!"