To specify fields to check for duplicate records
1 From the Edit menu, click Define Fields (note that all users must be logged out as the database will be locked).
2 From the Record Type list in the Advanced tab of the Define Fields dialog box, select Contact or Group.
3 In the Match Duplicates Using group box, select up to three fields that ACT! should compare when searching for duplicates.
4 If you want to be notified when you enter a duplicate contact or group, select Enable Duplicate Checking.