Geoprocessing

Online help: http://webhelp.esri.com/arcgisdesktop/9.1/index.cfm

Different ways to do geoprocessing in ArcGIS

1. Basic stuff the buffering in ArcMap
2. From ArcToolbox in either ArcMap or ArcCatalog
3. Command line, either a shell or from a command window in ArcCatalog; if you run it in an ArcCatalog window it helps you type the right args. Not quite sure why anyone would want to use the command line this way...
4. Model Builder can be used to invoke standard tools or to call your scripts.
5. Scripting usually with Python, then calling scripts from one of the above methods.

TIPS

ArcCatalog Tools->Options->Geoprocessing

Check the box to allow overwriting of files, so that you don't end up creating numbered files like water_1 and allstreets_3

Set your default tools directory to something reasonable.