Planning a site is a major task and there lots for you to think about here and many questions to ask yourself before you jump right in. Doing it right the first time is way faster than having to do it all over.
A major factor in determining your success is the amount of time you take to carefully plan your site and to educate yourself. Please don't take this point lightly, as it can literally mean the difference between your success and failure. You should understand and be informed of the technologies being used to create your site. They are many technologies that can be used along with various requirements and and various associated costs. Hosting costs, maintenance costs, copyright issues, promotion and security are all important issues that need to be addressed as you plan your site.
If you read through some of the material I have prepared, you will find much of the information is a "must know" and it will help you to get started on the right track.
Now on to your next step which is web strategy.