The most basic level of doing business on the internet is to allow people to get in touch with you. This is typically a page on the website called Contact Us. Here are some basics of having an effective contact page.
If you have a traditional brick and mortar physical presence, list your physical address.
If you're a home-based or virtual business, list your business mailing address, which is typically a Suite Number (Box number) at a mailing locaiton such as the UPS store.
List your primary contact phone number and what your normal business hours are.
Should you list an email address? Some like to do so, others fear it will bring more spam. Either have a clickable link to your email address or a simple contact form with the person's email address, subject and text of the body. Your website should email you the contents of the form. Spam may be an issue here as well, so you may have to add a captcha to prevent programs from filling it out.
Homework
Can users find your contact form easily?
Can users easily fill out that form?
Have you recently run a "dry run" and filled out that form to make sure it's getting to whom it needs to go?
How many contact forms were filled out this past month?
Were they followed up?