Your website may need to do more than one thing but it's vital that each function is clearly understood and cleanly executed in a separate part of the site.
Write down clearly who your visitors will be and what you want them to do.
What are the goals for your website?
How will it earn you money?
It is generally accepted that you only have 5 to 10 seconds to convince your visitors to stay before they will go elsewhere.
Therefore it's vital they can find what they are looking for or something of interest immediately.
Visitors initial eye contact is in the centre of the page just below the top graphic. Make sure you put your most important information there.
Visitors often scan for things of interest. Large text headings for each paragraph make it much easier to find what they are looking for.
Websites are software and no one likes having to learn different software. Copy existing layouts so that people already understand how to use them e.g. top, side and bottom menus.
No one method of navigation will suit everyone so make sure links are available in a number of places.
Remember, the more difficult it is to find things the more people you will lose.
Marketing experts believe that up to 75% of purchases are made with people's subconcious desires. That may be so but over-designing is one of the easiest way to make a website under perform.
It's true that clients buy websites based on the feel good factor of what they look like but this does not always follow through to how well the website sells. Certainly the product inside the website needs to look good and if this is a fashion item or similar then the desireable image must be carried through, however, fussy, over-designed sites can distract the visitors eyes and may make it more difficult to navigate.
Certainly make sure the site looks good but remember that visitors may not stay on the site for long. Keep the site simple and easy to read so that the visitors only look where you want them to look and find content to take them to your goal.
Use this form to help understand and plan your website
Note how the design and visual approach must fit in with the purpose and function. Not the other way around.