Summary:
How understanding your audience's needs and expectations can help you choose the right tone for your site.
It is extremely difficult to design a site without any knowledge of who will be using it and what their needs and expectations are. If you can get a clear picture of what your target audience is like, what makes them interested and engaged, then you've won half the battle of making a good Web Site.
One thing you can ascertain at an early stage is whether your audience is going to be very diverse (e.g. the entire student population of a university) or whether you're talking to a specialised group (e.g. engineers). The more diverse an audience the greater the need for a design that has general appeal (which may or may not be restricting). The more specialised the group the greater the need to address the specific concerns and expectations of that group. If its not obvious then help yourself by generating a series of words that describe the kind of site you think might be appropriate for your audience and then go on to choose a design theme, colours and photographs based on those descriptions.
Inspiration for Web Site designs can come from many sources - sites on the internet, magazines, books, TV, art, nature, science, geometric shapes and other aspects of our day to day environments. Experienced designers will have a huge reservoir of images and ideas in their heads to draw upon but the beginner shouldn't be deterred as a quick trawl of the internet might yield an idea which can be adapted to suit your needs. Remember that sometimes a practical design may be more appropriate than something fancier. A library Web Site might emphasise functionality whereas an art society Web Site might be more influenced by the colours and shapes in works of art.