Designing the look and feel of your site is an ongoing process.

You probably had several ideas before you started the design  process. Those ideas may have changed as you defined your goals,  identified your audience and organized the structure of your web site  into content lists and storyboards.  That's as it should  be.  The ideas you start out with  shouldn't be inflexible but should change and adapt  to the emerging design.

But what if you still don't have any strong ideas about the look and feel of your site?  Now is the time to make these decisions. What kind of thing do you and, more importantly, your client have in mind?   

One thing you can do is look around the web at how other people have designed their sites.  Notice how they lay out their text and graphics and how that affects the information presented.

A minimalist approach with a small amount of text and graphics carefully laid out on screen can be very  sophisticated. The extrovert look has lots of  graphics, icons and text filling the screen from  corner to corner. It's dramatic and dynamic when
handled well.   Just remember you trying to create a site that delivers conveys knowledge to someone else as easily and efficiently as possible.

The content of your site can frequently guide your design process.  Is content very graphical in nature, or will you a have a lot of text?   

The only way to be sure that your design presents the information in the way that you intend is to try to test your site with a few of the people who think will be using it.