Bugzilla is configured by changing various parameters, accessed from the "Edit parameters" link in the page footer. Here are some of the key parameters on that page. You should run down this list and set them appropriately after installing Bugzilla.
maintainer: The maintainer parameter is the email address of the person responsible for maintaining this Bugzilla installation. The address need not be that of a valid Bugzilla account.
urlbase: This parameter defines the fully qualified domain name and web server path to your Bugzilla installation.
For example, if your Bugzilla query page is http://www.foo.com/bugzilla/query.cgi, set your "urlbase" to http://www.foo.com/bugzilla/.
usebuggroups: This dictates whether or not to implement group-based security for Bugzilla. If set, Bugzilla bugs can have an associated 'group', defining which users are allowed to see and edit the bug.
Set "usebuggroups" to "on" only if you may wish to restrict access to particular bugs to certain groups of users. I suggest leaving this parameter off while initially testing your Bugzilla.
usebuggroupsentry: Bugzilla Products can have a group associated with them, so that certain users can only see bugs in certain products. When this parameter is set to "on", this places all newly-created bugs in the group for their product immediately.
shadowdb: You run into an interesting problem when Bugzilla reaches a high level of continuous activity. MySQL supports only table-level write locking. What this means is that if someone needs to make a change to a bug, they will lock the entire table until the operation is complete. Locking for write also blocks reads until the write is complete. The "shadowdb" parameter was designed to get around this limitation. While only a single user is allowed to write to a table at a time, reads can continue unimpeded on a read-only shadow copy of the database. Although your database size will double, a shadow database can cause an enormous performance improvement when implemented on extremely high-traffic Bugzilla databases.
As a guide, mozilla.org began needing "shadowdb" when they reached around 40,000 Bugzilla users with several hundred Bugzilla bug changes and comments per day.
The value of the parameter defines the name of the shadow bug database. Set "shadowdb" to e.g. "bug_shadowdb" if you will be running a *very* large installation of Bugzilla.
Enabling "shadowdb" can adversely affect the stability of your installation of Bugzilla. You should regularly check that your database is in sync. It is often advisable to force a shadow database sync nightly via "cron".
If you use the "shadowdb" option, it is only natural that you should turn the "queryagainstshadowdb" option on as well. Otherwise you are replicating data into a shadow database for no reason!
shutdownhtml: If you need to shut down Bugzilla to perform administration, enter some descriptive HTML here and anyone who tries to use Bugzilla will receive a page to that effect. Obviously, editparams.cgi will still be accessible so you can remove the HTML and re-enable Bugzilla. :-)
passwordmail: Every time a user creates an account, the text of this parameter (with substitutions) is sent to the new user along with their password message.
Add any text you wish to the "passwordmail" parameter box. For instance, many people choose to use this box to give a quick training blurb about how to use Bugzilla at your site.
useqacontact: This allows you to define an email address for each component, in addition to that of the default owner, who will be sent carbon copies of incoming bugs.
usestatuswhiteboard: This defines whether you wish to have a free-form, overwritable field associated with each bug. The advantage of the Status Whiteboard is that it can be deleted or modified with ease, and provides an easily-searchable field for indexing some bugs that have some trait in common.
whinedays: Set this to the number of days you want to let bugs go in the NEW or REOPENED state before notifying people they have untouched new bugs. If you do not plan to use this feature, simply do not set up the whining cron job described in the installation instructions, or set this value to "0" (never whine).
commenton*: All these fields allow you to dictate what changes can pass without comment, and which must have a comment from the person who changed them. Often, administrators will allow users to add themselves to the CC list, accept bugs, or change the Status Whiteboard without adding a comment as to their reasons for the change, yet require that most other changes come with an explanation.
Set the "commenton" options according to your site policy. It is a wise idea to require comments when users resolve, reassign, or reopen bugs at the very least.
It is generally far better to require a developer comment when resolving bugs than not. Few things are more annoying to bug database users than having a developer mark a bug "fixed" without any comment as to what the fix was (or even that it was truly fixed!)
supportwatchers: Turning on this option allows users to ask to receive copies of all a particular other user's bug email. This is, of course, subject to the groupset restrictions on the bug; if the "watcher" would not normally be allowed to view a bug, the watcher cannot get around the system by setting herself up to watch the bugs of someone with bugs outside her privileges. They would still only receive email updates for those bugs she could normally view.