For this article, I'm going to assume you've managed to get Joomla installed on your website host and now you're looking around in the back end and unsure what to do next.

The first think you'll want to do is decide on your websites structure.  You're going to have topics you'll want to cover with your website such as what the site is for, what services you provide, what news you want to get out, etc.  These will roughly equate to the 'Sections' on your Joomla site.  Some of your content may be static - it never changes - or you may decide to skip Joomla's Static content feature and just use the sections and categories to help you maintain an organized structure.

Once you have a solid idea of what content sections and categories you might need, you can start entering them in.  Your site structure might look something like this:

Section - Products

    Categories - Widgets, Widget accessories

Section - Services

    Categories - Widget maintenance, widget installation

Section - About Us

    Categories - Press Releases, Staff, History, Testimonials

Next, you might want to think about any extensions to Joomla that would add extra functionality to your website. If you're running a business related site, you might want a component for more detailed lead generation forms, newsletter subscription, link directory, etc.  If you're running a community site, you'll want the Community Builder component that allows your site members to have rich profiles for display on your site.  You might also want to add forums, an event calendar and more.

There are also many extensions available that will help you manage your Joomla site much easier such as the JCE editor - a great component for editing the content on your website, JCE has plugins for easy image upload, etc.   

You'll also want to consider making your Joomla site search engine friendly.  Good SEO (Search Engine Optimization) is crucial if you want Google et. al. to find your website and rank it well.  I'd recommend the OpenSEF extension as well as the new Meta tag generator component.

That's a good way to get started!  Next, I'll cover how to choose a "look and feel" for your website and how module positions work.