Getting Started

The Drupal installation isn't really any different than other uses, so I won't detail that here.  You DO need to make sure you enabled the forum module in the Drupal core (and any other modules that you might need, such as upload, profile, search, poll, tracker, etc.)

Gather Required Modules

Please note that not all of these modules may be necessary for your site.  In fact, you can just enable the forum module and go with that!  I'm attempting to detail my process here to help others (and to help myself if I ever need to reinstall.)

The following is a list of modules that I added to get the forum working the way I needed:

• phpBB2Drupal (absolutely necessary for migrating from phpBB, but otherwise you probably won't need it.)
• BBCode (allows using BBCode for text markup.  Common in a lot of forums, so it's a good idea to have.)
• Privatemsg (needed so users can send private messages.  phpBB2Drupal uses this to convert phpBB PMs.)
• phpass (stores passwords securely.  Needed by phpBB2Drupal, but make sure to read over the project page!)
• Comment Upload (allows attachments to be included with comments.)
• Better Formats (Drupal doesn't natively allow an input format to be used for just one content type.  This fixes that since you might not want your forum type to be used for blogs, or tutorials... then again maybe you do.)

The following improve the forum experience:

• Advanced Forum (gives the Drupal forum a look closer to other, more common forums.)
• Author Pane (provides a block of information about the author.  Required by Advanced Forum.)
• Flatcomments (forces comments to always reply to the node regardless of the reply link used to post the comment.  Required by Advanced Forum.)
• Forum Access (allows forums to be set to private.  This may be included in the core of Drupal 7.)
• ACL (required by Forum Access.)
• Signatures for Forums (allows signatures to be placed in the posts.  If a user changes their signature, all posts will be updated.)
• Smileys (converts ASCII emoticons to graphical smilies.)
• Fasttoggle (provides links for moderators to directly change post settings.)