Many sites don't really require instructions. But as companies move more of their business out to the Web, we often expect the customer to do more "self-servicing".
We now require that well-designed site must be self-aware and self-evident. Such guidance can be provided through good visual design, well-written intros, context-sensitive popups and engaging, appropriate mini-presentations.
Frequently Asked Questions show that you understand the situation. "I anticipate your question. Here's the answer."
Quick, easy answers
New visitors to a site often go to the FAQ's section as a shortcut introduction. Including FAQ's prominently as a regular part of site design can be helpful.
In addition to a dedicated index page of FAQ's as a menubar link on the site, a context-appropriate FAQ link should appear on any page where it's relevant. It opens the FAQ popup window and links directly to the appropriate answer anchor.
I like to present the FAQ answers in a separate window popup, so that you can invoke this valuable page of help information from anywhere on the site and still not lose your context.
The ideal content of an FAQ section is a list of the problems that users most frequently face - in other words, they are usability issues that haven't yet been addressed yet in the design.
The Call Center is often a guide to FAQ's ... and Design
If you find you've got a bunch of FAQ's focusing on a particular topic, then you may want to create a mini-presentation video Tutorial.