Using filters you can delete contacts from a group based on a filter of your choosing.
Say for example you have uploaded a list into a new group and you want to delete the contacts from that group who are already in your account in other groups. Leaving you with a group of brand new contacts. Perfect for sending welcome and introduction emails to brand new contacts.
Once you have uploaded the list. Open the new Group so that the contacts display on the screen.
Use the filter with the following criteria:
Field - Date Added
Operator - Before
Value - "the date you uploaded the contact file"
Select the email addresses now displayed. Remembering to click the Select all button.
Under Actions select "Delete from This Group".
Clear the filter from your group. What you will be left with is a group of clean contacts who have not received an email from you before. Perfect for sending welcome and introduction emails.