You've been well covered here, but another way is just to write as if you're talking to someone. Fix the grammar and punctuation after. :)

I struggled with this at first, research is your friend. Come up with some good keywords for your posts, then do a Google search on the keyword. Then view some of the high ranking sites with your chosen keywords, to see how they write. In other words, learn by example.

You don't want to copy people though, originality and quality is important also, but getting ideas from others is how we all start out.

If you know what you want to write about, put it in here....

http://ubersuggest.org/

It will give you a lot of suggestions for topics based on your chosen subject or keyword/phrase. I find by using this I end up with about 5 post ideas from the one keyword.

It's a steep learning curve deciding what works best for you, so just play around with it, you've had a few ideas given to you by the other replies here also :)

This will also help you out: How To Write a 500 Word Article (The Easy Way)

There are several different factors that play into writing a "good post". Take a look at posts in your niche that have been shared a lot or have a lot of comments and see how it is written. Is it in list form? (22 Reasons Why...) Is it cachy? (You Won't Believe What She Said When...) etc.

What I like to do is break things up with H2 tags like this:

[title]

[intro text]

[h2 subpoint]

[text]

[h2 subpoint]

[text]

[h2 subpoint]

[text]

[conclusion subpoint]

[outro text]

You'll also want to incorporate images into your posts too.

Biggest thing that will help though is looking at the competition and see what makes their posts so successful and borrow a little bit from their framework.

I hope this helps a bit as your question was a bit vague lol

I personally do not use this approach by some members have. Hopefully they will see this and respond.