If you are using ArcMap, you can manually change the zoom level of the Extent Indicator to get started, then set it to an automatic mode . Here's what you do:
1. Look at the Table of Contents for the Extent Indicator Data Frame. It is usually defaulted to "New Data Frame" but may also have been renamed.
2. Right-click on the Extent Data Frame name in the Table of Contents and choose "Activate"
3. You can now use the zoom tools to zoom in or use the Map Scale pulldown (or manually type in the map scale)
4. To make this more automatic, one can also go to the Data Frame tab and set the Extent to Fixed Scale or one of the other options.
Note - if Data Drive Pages are being employed, there are some other options (though that's another major discussion in itself).
Chris Donohue, GISP