To create a commercially viable website, you need to formulate a good website idea or theme.  The subject for your website ought to be something that you are interested in and knowledgeable about.  The theme of your site should be focused around something you want to research and explore.  To be successful, your work truly needs to be a labor of love. You do not need to be an expert in the subject area.  You do, however, need to know more about the topic than most others do. 

The theme for your website could be something related to work, family life or a personal interest.  The topic need not be of broad general interest.  In fact, great success can be attained with a narrow, specialised website topic, where your competitors will be few in number. You can begin your website by focusing on a niche market and by growing the site to attract a broader audience.  Always remember that your potential audience is global and not limited to your community or country. 

Once you have selected a suitable subject area for your website, give some thought to how your website can be grown.  Growth can occur by delving into greater detail in the subject area or by broadening the subject area into related fields.  In general, however, think of your website as a store, with each web page as a product in that store.  Your goal is to attract people to your store by offering a specific item and hoping that they will buy items they had not planned on purchasing.  Load your store with complimentary items and bounce your visitors from one department to another.  

If you can visualize a growth strategy for your site, before you purchase a domain name, you will then be able to select a web address that is narrow enough to attract people and search engines but broad enough not to restrict your future growth.