Developing a website is not unlike building a house...
You need to have a solid design based on your needs/wants and then you hand it over to a builder to complete the job. If the job is not scoped out correctly before work begins or design changes are made halfway through the project, this can lead to delays.
Have a look at your main competitor's sites, search google for what you're selling/advertising and take note of what's on offer from the sites that come up on the first page of the search results.
Once you have an idea of the functionality and maybe the look & feel of your site, it's always a good idea to check some of sites on the web that offer website templates for purchase. I recommend Shape5, Rockettheme, and JoomlaXTC for their Joomla templates.
I make these recommendations because I develop websites using Jooma, a template-based content management system (or CMS). This allows me to develop sites that my clients can then manage once the site has been launched. Everything from the colour scheme, to the site images and content can be controlled easily with a good CMS.
When looking at templates, keep in mind that they are often crowded with information, boxes, and content. My preference is to take a template with the right combination of functionality and aesthetics, and then remove everything that is not necessary - the aim for any website should be to create a clean and simple site that does not overwhelm viewers with content, jarring colours or difficult navigation.
If you do not have a strong feel for what the site should look like, the functionality it should have, or the content you need, that's ok - I can put together a proposed site fairly quickly for you to approve and/or make changes to.
If you know exactly what you want, fantastic! Let me know and I will create a site mockup for you to critique.
The devil's in the detail with your site template. Just like a house, it needs to be perfect or you'll either a) put up with something that isn't right for you, or b) spend unnecessary money afterwords in re-doing work that should have been done correctly in the first place.