Source: eGrabber Newsletters
Did you know that you can schedule activities in ACT!, that will be invisible to other ACT! users? You can hide an activity from other ACT! users by scheduling it as a private activity.
Here's how you can do it:
1. Select Preferences >> Tools from the menu
2. Select the Calendar & Scheduling tab
3. Click on the Scheduling Preferences button
4. Uncheck the 'Make new activities public' option
5. Click OK
Now, any activity that you schedule will be hidden from the other ACT! users.