Understanding the type of people who visit your site is a very important task because you can use that information to enhance your site to suit them. As a result, you will gain more loyal returning visitors that come back again and again for more.
What is the age level and what kind of knowledge does your audience have? A layman might linger around a general site on gardening, but a professional botanist might turn his nose at the very same site. Similarly, a regular person will leave a site filled with astronomy abstracts but a well educated university graduate will find that site interesting.
Take your audience's emotional state into consideration when building your site. If a very irritated visitor searches for a solution and comes across your site, you will want to make sure you offer the solution right up front and sell or promote your product to him second. In this way, the visitor will put his trust in you for offering the solution to his problems and is more likely to buy your product when you offer it to him after that.
When you design the layout for your site, you have to take into account the characteristics of your audience. Are they old or young people? Are they looking for trends or are they just looking for information served without any icing on the cake? For example, introducing a new, exciting game with a simple, straightforward black text against white background page will definitely turn prospects away. Make sure your design suits your site's general theme.
Try to sprinkle colloquial language in your sites sparingly where you see fit and you will create a sense that your audience is on common ground with you. This in turn builds a trusting relationship between you and your audience, which will come in useful should you want to market a product to your audience.