I have done this before... actually just a few months ago, so I'm only adding a few edits. I'd like to touch on writing effectively and well for the web (more specifically blogging, but a lot of this can be applied to copy writing). Clients often struggle with using a blog, but you shouldn't really blame them for it. Someone might have told them it's good for them and given them one, but who said everyone knows how to write or what to write about or why they're writing in the first place? I hope to point a few of the lost in the right direction.

What to Blog About?

What moves you? Or what do you think will move other people? What is useful? What is relevant? What is interesting? If you don't know the answer to any of those questions, then don't try. Fitting any of those categories can be enough to qualify, but without that qualification, you have made your post a burden and an annoyance to readers. News, tips, and personal thoughts are all perfectly acceptable as long as they fit with one of those questions.

What Format?

Aside from a few exceptions, begin with some sort of introductory paragraph or sentence. This keeps readers from wasting their time, so they know if they've found exactly what they're looking for. Whether you make it epic or to-the-point is completely up to you. Either is fine.

The rest all depends on the content, but just be logical. If you are sharing a short story you came up with, write in traditional format. Most posts, like news, will be similar. Break sections and use headings properly. Before you begin think about what pieces of the post go together well and clump them accordingly. If you list features, use bullets. Number instructions. If you have a big quote, block it out.

Closing is also completely up to the content and writer. Most choose to take a final summarizing stand, in a way bringing the post all together. Some choose not to waste their time closing at all. No one will rebuke you either way.

Which Style?

The more formal and distant a post can be, the cleaner and easier it will read. This does become a problem as blogging does have a personal aspect to it, with writers having their own opinions. First person is perfectly fine if it is relevant. If you are describing an experience you had, go right ahead. Your readers may know you personally anyways. Second person is extremely difficult to avoid and can be a pain because of that darn personal feel. The key is to be consistent. Don't switch from "one" to "you" in the middle of a post.

Personal writing style is an issue of its own. If you represent a company or organization, try to curb it as much as possible. If you aren't the most eloquent of speakers, please don't write like you talk. Personal blogs are truly their own animal and can be dealt with however the author deems, with no questions.

No-Nos You May or May Not Know and Other Pointers:

• Don't begin sentences with "and" or "because".
• Plural words that end in an "s" do not use apostrophes. Correct: "dogs" Incorrect: "dog's". (See title of this section and refer to proper format of "No-nos".
• "Its" is possessive. "It's" = "It is".
• When a non-plural or plural word that ends in an "s" is possessive, it looks like these: the puppies' tales, the Smiths' house, Jonas' hat (My friend Jonas has a hat. It's Jonas' hat).
• Spell and grammar check. Just do it. This goes for personal blogs as well; people DO notice, even if you don't.
• The only way to punctuate properly is to just learn. Do you know how to use semicolons correctly? If you missed that day in English class, Google it!
• Check your word repetition with Command+F (Ctrl+F on Windows). Did you use the word "dynamic" in three sentences in the same paragraph?
• "Alot" is not a word. "A" and "lot" are both words.
• Spell out single-digit whole numbers as well as simple small fractions (like "two" and "one-half", respectively). Also, be consistent with number formatting.
• They're over there. That's their movie ticket.
  

Writing Effectively

This is important to understand for the sake of readers and that of search engines. The most important thing to remember is to write for people. Key-word stuffing to the point that it impairs readability is absolutely unacceptable and actually detrimental to page rank. Writing solid, useful content is what makes a blog worth visiting, and readers respond to that. At the same time, if you would like to be found on search engines for certain terms, just be smart and use them where you would anyways. If you find yourself going back and trying too hard to add words in, you're probably just about to cross the line.

On a related note, using adjectives in desperation as an attempt to sound smarter or fill in space does not fool readers. If there is little to say, say little. Less room for fluff means more room for teaching and/or learning. This is of course not to say that adjectives aren't cool and don't effectively convey thoughts. Just please don't abuse them.

Length

To close, I touch on length. Just get the point across! If there's a lot to say, go ahead. If not, don't waste readers' time trying to bulk up.