There are several ways to remove people from campaigns:
From the Menu:
Go the person’s record and select File / Remove from Campaign.
Edit the Campaign:
Go to the Campaign Manager and edit the campaign. Click the Target List tab and remove the person from the list.
If you created the Target List using a query, you can rerun the query and select Remove People Only from the options. People not selected by the query will be removed.
Viewing Campaign Status:
Go to the person’s record and select View / Campaign Status. Then click Remove.