For Systems 6, 7 and Mac OS 8.x:
Automatic log on can be disabled by dragging the AppleShare Prep file (System Folder: Preferences: AppleShare Prep) to the Trash. Removing this file will eliminate automatic log on for all server volumes. Restoring automatic connection to specific server volumes at startup can be accomplished in the usual fashion.
For Mac OS 9/AppleShare client 3.8.5 & higher:
Automatic log on can be disabled by dragging to the Trash the server's alias that has been placed in the Servers folder in the System Folder. Each server that mounts at start up has a corresponding alias in the Servers folder.
Note: Some third-party software, such as Suitcase, will also attempt to mount remote volumes at startup. The third-party vendor should be contacted for instructions on disabling automatic log on with such software.