Question: What is the best or common way to implement FAQ page on a SharePoint Site collection?

Answer: 
What we've done in the past:

1. Create a custom list
2. Rename the Title column to Question
3. Add a new Column of type Multi-Line Text and name it Answer
4. Modify the default view to only show those 2 columns and set the style to Newsletter

You end up with something like:

![alt text](https://i.stack.imgur.com/Mhw0l.png)

You can then place this on a page using a listview webpart.

**Update:** I've written this up on my blog with a SharePoint 2010 example here: <http://thechriskent.com/2012/03/09/simple-sharepoint-faq-in-5-minutes/>
Another possible solution -- using the Preview Pane style option, you can end up with a list of questions in a left hand column and mousing over shows the (selected) fields.

I have Q's with long answers, so I think this may work better in some situations (until it can accordion at an individual record level or on a certain field).

![enter image description here](https://i.stack.imgur.com/zUMnE.jpg)