This is my guide to writing guides. This is a new one, so there will be very little editing before it goes up, and thus there won't ba any changes and additions. Now, always bear in mind, I am not a published author or professional critic, I am here on the same website as you, and thus I most likely don't know anything more then most of the other writers on this site. These guides are for the inexperienced writers who need a few tips and for those here who quite simply are bored and have nothing better to do for a few minutes but read them.
This may not seem major, but it's very important. You need to make sure people know that it's a guide, and not make yourself seem stuck-up and pretentious in it. Calling it something like The GOOD writer's guide is a really bad idea. It implies that all writers who do not follow your guide are bad writers, which is unfair and completely incorrect. Heaven knows most published authors would scoff at me is they saw these guides.
I always put them in. It doesn't need to be anything major, just a little 'you don't have to follow this if you don't want to' at the beginning or the end. It's also a really good idea to mention somewhere that reading the guide will not instantly make you a top class writer, and that you are only making suggestions and giving advice, not setting out the rules on writing. Just mentioning this to the reader is always a good idea.
You DO NOT know everything
If you're reading this guide, I assume you've not yet written a best-seller. You may still do so, but if you have already then we have this situation backwards. Few things are more annoying than when somebody claims to know everything about a topic when they're at the same stage as the rest of us. This is what the disclaimers are for. Always make sure to remember that you aren't infallible while you're writing the guide.
Make your own works available to view
If you don't want to put you current Work-In-Progress up here, then fine. But if you're writing guides to writing, please make at least a short story or two available to readers, so that they can judge for themselves whether or not they think you know what you're talking about. I've seen a few people in the past put guides up, without having posted up any actual story. For all I could have know, they may never have written anything in their lives. I didn't take them particularly seriously, to say the least. Now, you don't have to have a ton of stuff up, but just a few short pieces are good for the reader to see how your advice works out for you.
Dos and Don'ts
...Are extremely unreliable. Don't use a characters name as a title? The Great Gatsby, Eragon, Moby Dick, Artemis Fowl, Harry Potter, Othello, Romeo and Juliet (most of Shakespeare's works, actually)... Yes, I did once see this example. And all of the books I've listed have been very successful, and many are even used to teach English Literature. Any straight out Dos and Don'ts can easily be proven wrong, so it's best to ovoid them. Just saying something is a good or bad idea isn't a problem, but don't outright tell somebody not to do something else their writing will suck. Unless we're talking about anti-Sues, which are a definite DON'T (sorry, couldn't help myself)
Spelling, Grammar and Punctuation
Respect the language in which you write. Spellcheck guides, and make sure to ovoid as many glaring grammatical errors as you can. Punctuate properly. I know my spelling isn't the best, and for that I apologize - I do try, but I have real problems with spelling things. Mostly, it's stupid mistakes. But if you're trying to give people advice on how to write, misspelling a three letter word is just in bad taste. A little bit of effort goes a long way, after all.
Let's not forget the customary disclaimer: I know nothing. This is advice, not rules. Nobody made you read this, and I'm afraid you can't un-read it. But that doesn't mean you need to pay attention to it. I actually put in the effort to spellcheck this one, which may or may not qualify as a miracle.