First of all, I recommend that you read the other writing guides on SOL's homepage. All are very good, and Phil will give you a laugh, or two. For advanced writers, I highly recommend "Elements of Erotic Literature". Pleasure Boy 1 has put together an astoundingly good guide.
I have found that the most common mistake writers on SOL make, is writing sentences, that keep going, and going; until you are about to tear the hair from your head, in complete frustration, as you try to figure out: "Just what in the hell are they talking about?"
Sort of like the above sentence. :)
Even when properly punctuated, they really detract from your story's content (and they are seldom 'properly' done, which adds to the frustration felt by the reader).
The second most common mistake, is posting too soon. A 7KB Chapter One, posted by itself, does not give the reader 'enough to chew on'. It varies from story, to story; but I recommend you not post less than 30KB, at first posting. This of course, does not include 'Short Shorts', where the entire story is less than 30KB.
On punctuation: 'Use it, but don't abuse it.'
If you have the slightest difficulty with punctuation, consider breaking the long sentence, into two sentences.
Like this:
You might have some difficulty with punctuation. Making two sentences could be better.
A good 'rule of thumb' is: "One thought, one sentence."
Remember, if your sentences ramble, so will your reader.
And you don't want that.
You want the reader to be engrossed in your story. You don't want him mired in incomprehensible, 'long winded' sentences.
Moving on.
I try to use more periods, than commas; more commas, than semi-colons; and more semi-colons, than colons. This, of course, means that I almost never use colons. In fact, about the only time I use a colon, is before a list of items.
"The grocer brought to me several kinds of lettuce: Romain, Iceburg, Leaf Lettuce, etc."
Note that there is no period after etc. When a sentence ends in an abbreviation, no period is used. The abbreviation's period is sufficient.
Quotes.
This is probably the most misused item in the English language.
Look at these examples.
"I really like it."
This is simple, and straightforward.
"I really like it," he said.
Note that the "quote" ends with a comma, and 'he' is NOT capitalized. The error of ending a quote with a period, and capitalizing 'He', is so common. It's really frustrating, when I try to read a story.
"I really like it," I said.
"I really like it," Joseph said.
Proper names, and personal pronouns, remain capitalized. Note, however, that the "quote" still ends with a comma.
John said, "I really like it."
This format can be used, occasionally, to break the monotony of:
"I really like it," John said.
If used improperly, it is confusing. If a complete sentence is placed before the "quote", you end up with two sentences, trying to act like one.
John looked at her, raised his eyebrows, and said, "I really like it."
This works, but a better way is as follows.
John looked at her and raised his eyebrows.
"I really like it."
Note that you eliminate two commas, and the "quote" stands by itself, where it belongs.
"Where it belongs?" you ask.
"Yes, indeedy!" I respond.
A "quote" has but one purpose: expressing the words of your character (Yes, I used a colon. This is the only other case, where I would use one.). Also note that 'you' is not capitalized, yet 'I' is. That is because, in English, 'you' is not a 'personal pronoun' as it is also used to describe many people.
In most other languages, there is a separate word for the personal 'you', and the impersonal, or polite form of 'you'. For instance; in French, 'tu' is the personal pronoun, while 'vous' is for everything else. English does not have this.
Yes, I agree. This is one of the few drawbacks of the English language.
"I really like it," he said. "It's really great!"
Note that this is two sentences. "I really like it," and, "It's really great!" That is why there is a period after 'he said'. When the quote is resumed, it must begin with capitalization, as it is a separate sentence. "It's really great!"
One final item.
Using a Spell Checker is a very good idea. However, a spell checker won't tell you when you type the wrong word. It won't tell you that 'site' is wrong, when you meant to write 'sight.'
So, when you are re-reading your work for errors, remember to check for homonyms (words that sound the same, but mean different things). To, too, two. That's a prime example.
Good luck, and remember that writing is evolutionary. The more you write, the better you will get at writing!