Focus first on what you are trying to achieve then thinking of your audience first is the most important thing. Focus then on making your website appropriate for that group of people.

As an example suppose you are developing a website for potential knitters - think of what knitters would require in a website... what would attract them? what would keep them coming back? Good luck!!

In my opinion simple is almost always better. It's also really important to establish an excellent template and then use that to construct your site - it will save you tonnes of time later.

Don't use themes for your website that conflict with your subject.

For example, don't use flowers on a website called Know Boats whose subject is knowledge and advice