This is one of those things I think of every time I see something I consider to be poorly structured, and something I think is a requirement for long prose.
Tip #14: Learn how to use hated punctuation.
Semicolons, colons, dashes, and ellipses must be the loneliest punctuation marks out there in the big world of English grammar. I use all of them on a regular basis; they're pretty handy.
Semicolons are a comma/period hybrid, even in appearance. They're way easier to use than most people seem to think. The semicolon is used in those awkward sentences that would be a run-on if you used a comma, but would seem broken up if you used a period. Examples:
"It's not that it's too heavy; it's just bulky."
"I didn't get a chance to wash the dishes; they're still there."
Colons aren't quite hated, but they're certainly misused. I think the biggest rule about colons is they never follow a verb. "The following items I need are:" is not a proper use of a colon, yet that's the way many writers use them, from what I see around DeviantART and such. Proper usage of a colon actually varies quite a bit because the examples are so specific, so if you're curious, take a look over on Wikipedia. Just for the record, I don't like the use of a colon in independent appositives. I think a semicolon looks much more intelligent. To me, using a colon seems like you aren't really sure what you're doing. I've never seen it in published writing.
Dashes are, in my opinion, a really good way to establish a voice in your writing. They can break up a sentence for more impact, whether something is just that important or it's being said or thought by a character whose thoughts happen to be very muddled. They're another punctuation mark that has lots of uses, but in prose, they're really good for one thing - cramming extra stuff into a sentence. Examples:
"I went to the store - without you, I might add - and got those billion things you wanted."
"Every time you laugh - even when you just smile - it takes my breath away."
Ellipses are one of my favorites. They're another that adds voice to a piece of writing. Let me get this basic, simple, stupidly easy rule out of the way: three dots; no more, no less. I get where a lot of amateur writers are coming from when they make an ellipsis with twelve dots. It's a longer pause in their head, so it should be more dots...right? No. English (most languages, probably) doesn't work like that. The rules on spacing varies, but as a general rule in writing, as long as you're consistent, it never really matters too much. I never use a space on either side of the ellipsis, but there are a multitude of spacing options considered grammatically correct. Ellipses are used to indicate a pause, but they're different from commas. A comma indicates different clauses and should never be used solely for a verbal pause; ellipses can pop up anywhere. Examples:
"I just don't know...which one do you like better?"
"I...you...I don't even know what to say."
Ellipses, unlike a lot of other punctuation, can also be followed by another punctuation mark in certain cases. I've often seen an ellipses followed by a period for a total of four dots in a row, which I've done myself after seeing it in a lot of published books. Personally, I feel an ellipsis on its own isn't really a closing punctuation mark, but that opinion varies, and grammar rules are a little loose there. That's different than making an ellipsis four dots just for the hell of it. Examples:
"We're going where...?"
"She's just...I don't know...."
So there you have it. A few rules on some very neglected and misused punctuation marks.