Whether you have no website or are trying to redo a current website, it's worth it to think about what the goal is in updating the company's online image. The basics would be to generate new business, new contacts, and for customer communication. However, a website is simply another tool that any company can use and its uses are in no way limited to those few topics. For now, though, we'll go over those areas and hopefully get started down the correct path.
Generate New Business: In today's world, every business needs a website. Can you get by without one? Sure, but why? It's a tool that's available to everyone not just those people who know how to code. Statistically, people will search for a business online to learn about them before they ever consider buying a product. Therefore, generating new business is far easier with an online presence (which tends to be the case when people can actually find you...).
New Contacts: So these people found you, now what? One of the great things about having a website is collecting data from the potential customer (and this can happen anytime, day or night). Forms to collect potential customers are easy to setup and, in many cases, they can be linked into whatever contact management/email system that you're currently using. I know that this thought is nothing revolutionary, but I still run across sites, on a regular basis, that are not using a contact form, are poorly maintained, and are obviously not using all the tools available. Let the website work for you.
Communication: You got the attention of someone, now what? A website helps you to grow that relationship by putting out helpful content, alerting customers and potential customers of upcoming events or sales, and answering questions all while you're off doing any of the other task that have to be done to keep the business running. Helpful content could be in the form of how-to articles or videos. The site could be used to pass along an alert about important updates, closings due to weather, that you're at a particular event, etc. Of course, sometimes a customer simply has a question and maybe that question can be answered in a simple FAQ.
What to remember: These topics are a very high level overview of some of the very basic things that are possible. In other words, get started building and never stop because new amazing tools are constantly being developed.