As apparently not everyone is familiar with the latest achievements in typography, here's a quick and easy guide to punctuating your posts properly. It's simple, fun, and makes mods just so much less likely to go ballistic when reading the forum.
So, let's begin:
1. Fullstop
That little fella lives on the bottommost row of the alphabetic keys, a little bit to the right of M. On the same row you can also find his buddy, the Shift key. Together, they fight crime and help separate sentences. Note that fullstop is only that one key, it's not the long flat one at the very bottom, nor is it this funny ⏎ one to the right, though you still need both (read on to learn why!)
2. Comma
Now, with the basics in place, we can tackle the advanced topics. Comma lives right next to fullstop. With it, you can perform unheard of feats of clarity and grammatical correctness. How? Well, it's easy, you do it by observing the rules of English grammar, which in turn stem from the simple desire to separate clauses for easier reading and clearer structure. Such as in:
"In my opinion, comma is the best thing ever, maybe discounting fullstops."
3. Space, semicolon and return
Now we're talking sophisticated. Space is really useful, use it not only to separate words, but remember also to put one space after (not before!) commas and fullstops. With semicolon, you can build really complex sentences, full of clauses, that nevertheless stay readable and comprehensible. With return, you can advance to the next line. And what happens if you press it twice? That's right, you've just made a paragraph! Paragraphs are good, be sure to use paragraphs.
4. Question and exclamation mark
Now here's a mystery. Unlike all the other, neglected punctuation marks, those two get a lot of exposure, too much in fact. It might be confusing that both ? and ! have a dot in them, but don't be tricked, those are not just another way to spell a fullstop. Use them to pose a question or exclaim something, respectively. And remember that one of each is plenty enough already, you can't make things more questioning or exclaiming by stacking more punctuation on them. Or maybe you can, but then it becomes really shrieky, which hurts our delicate ears, and that in turn gets us all angry and likely to bitchslap you. So better don't.
5. Tips and tricks
When writing a post, you want others to read it, right? And if you want others to, why not take a moment and read it yourself, to make sure it resembles a well written post more than a stinky pile of dog poo? Believe me, stinky poo is no fun to read. And your intertubes could get clogged with poo, and that's just no good. So make sure you never send stinky poo, but always proper posts.