UPDATE: removing wiki markup.
Most of the Service Desk's we've set up at Twitter thus far are fairly simple:
* a button for each of the main components in a given project, this field is hidden on the form,
* most buttons use the Bug issue type, and
* they have the Summary, Description and Priority field on the form
For example: Screen Shot 2013-11-20 at 9.24.09 AM.png
The SLA's that Chris Lambert refers to are set up based upon the Atlassian doco: https://confluence.atlassian.com/display/SERVICEDESK/Reporting+on+SLAs
For example: Screen Shot 2013-11-20 at 9.26.08 AM.png
Finally, for the reports we have one chart for each SLA and sometimes there are multiple series on the chart. For example: Screen Shot 2013-11-20 at 9.29.56 AM.png
Blocker series setup: Screen Shot 2013-11-20 at 9.30.20 AM.png
If you need a hand let me know.