Extending your realtionship with your users can be as simple or as complex as you wish.

The best way to think of web based support is as an extension of your normal business or organisation ethos.

Whether you are providing an after sales service, information about current and past products, or advice about your area of expertise a support aspect to a web site can be invaluable in keeping your current users content, and assuring prospective users that you are commited to providing a service.

In some cases this might just be a list of answers to questions you are commonly asked, in other cases it may be an extensive list of instructions, or perhaps copies of your normal documentation and manuals.

This should not be viewed as a replacement for any other support mechanisms you may have in place, just an enhancement that will be greatly appreciated by your users. Many people will prefer to search a well designed web site to find support information, especially if they are unable to telephone you when you are available or writing a letter might take a long time to get a reply.

various strategies

Various different approaches are used to provide support.
Web site based information provided by the organisation commissioning the site is almost invariably a must, whether as flat pages or a searchable database.
There are other options as well.

Discussion forums - many manufacturers provide discussion forums for their products where users, and non-users, can post comments, ask questions and give each other answers and advice.
While there will invariably be a few negative comments posted this strategy can be extremely useful in gaining invaluable feedback. Of course as the site owner you are obviously able to remove messages you don't like, although heavy handed censorship might inhibit the use of such forums.

email discussion groups - like discussion forums the users are in charge by sending and receiving messages using an email server. These allow users to join an email discussion group and receive email messages sent to it by other users. While it is possible to have such lists moderated so that only the approved messages get sent, for an active group the work involved would become time consuming and the introduction of delays might inhibit free discussion and use of the system.
This form of self support is common for software products, research interests, support groups, service users.
While various companies allow email lists to be hosted on their systems these usually carry advertising placed by the hosting company.
To provide this type of service with your own identity and your own advertising/promotional messages (or no messages at all) requires the use of a "list server".
This can of course be arranged .