If you own a store, you learn what your customers want by asking them. "How can I help you?"
Wouldn't it be great if you could do the same with your Internet customers? If you knew what they wanted, you could publish more of it on your site and get better search rankings. Since your customers can't ask you what they want, they ask a search engine and the search engine answers by sending them to sites it considers has the best answer. If you knew the question, then you could work on the best answer.
In search engine optimization1 (SE0) your first goal is to address the needs of our visitors with relevant, useful content.
In other words, what do you write? It turns out that there are ways you can find out what's relevant and useful to your customers so that you can answer their questions and produce great content.
These post questions from people and depend on others for answers. The oldest and most used is Yahoo Answers. Go there and type in a category that's relevant to your market niche. Instantly you'll see what questions people are asking in the category. Also check out Ask Reddit and Amazon's Askville. These are less used than Yahoo Answers, but certainly worth a look.
Sometimes you can get a real sense of what's on people's minds and use your article to add to the conversation. A great starting place is Twitter. Open the site and type in your topic in the search box. Twitter has a good search engine and will let you use negating terms. For example, your topic might be 'bikes' but not 'motorbikes.' You'd enter 'bikes -motorbikes.' This drilling-down potential combined with Twitter's enormous sample size may get you to a real and unaddressed concern of your potential visitors. Expect to do some digging to eliminate many useless tweets.
StumbleUpon is a browsing site that let's surfers recommend sites to others. The site has been around and is very popular so you can see a wide variety of interests. The fastest way to navigate hot topics is from the address bar. Enter http://stumbleupon.com/discover/ANY WORD OR PHRASE THAT IS RELEVANT TO YOUR SITE. For example, http://stumbleupon.com/discover/mammogram.
The sites that come up reflect the concerns of the people who recommended them and can provide you with lots of writing ideas.
Another such site is Delicious, a social bookmarking site. Go there, click "most popular" and then enter the categories that you are interested in. What posts are getting the most comments? What posts could you write to contribute to the needs of these commenters?
Major Tip. Read comments. If you find a relavant post in your niche, read the comments. You may find more information about your market than from anywhere else.
This free service from Google will give you an approximate number of monthly searches for keywords and keyword phrases. Here you can see how many people are asking what questions. Find a hot keyword or longtail phrase and use it to search sources like Stumbleupon, Twitter, Delicious, and Yahoo Answers.