So first, what do I mean by good content? I mean that the articles, posts, and the things you talk about on your site should be four things: (1) unique, (2) useful, (3) enjoyable, and (4) frequently updated.
Unique
If your content isn't unique, then people don't have to come to your site to see it. They can go to a different site that has the same basic content. So when you create content for your site, make sure it's something unique that can't be found all over the Web. Then people will come to your site for that content.
Useful
If your content isn't useful, then it doesn't really serve a purpose. Maybe that's a good question to ask yourself when creating content--what is the purpose of this content? Is it to answer a question that people have? Is it to gather a lot of relevant links or ideas from several different places into one article? If your content is useful, people will read it.
Enjoyable
I like to read articles and posts that are entertaining and/or interesting. Is your article funny, or does it talk about an interesting topic? Write articles that people will enjoy reading.
I think some of the spelling/grammar/layout rules fall into this category too. If your spelling or grammar is bad, it can be distracting. Edit your article before you post it. If the layout is a huge block of unending text, people won't even start reading. Split it up into sections with headings and perhaps some images.
Frequently Updated
Keep your content fresh. Keep adding new content. If you have a blog, try to post often so that you don't lose your readers. People will stop coming to your blog if you don't keep posting on it. On sites other than blogs, keep adding new articles, tutorials, or whatever your content is. New content keeps people coming back, and it opens up new pages to be indexed by search engines.
Here's an example of a blog that I've been visiting lately because it has good content. It's called the Freelance Folder. The subject material is very relevant and useful to me as a freelance web designer. The links that they post to other articles and blogs are also very useful. And most of the posts are fairly interesting.

So I hope you've learned a thing or two about content and how it fits in with search engine optimization. In summary, if you have good content, people will read it.



