If you're cancelling a number of memberships at a time, this is the easiest and fastest way.
Go to Memberships > Reports.
Select the relevant Membership Level in the dropdown box.
This will show the list of Active and Partial Memberships under that Membership Level.
For each contact to cancel, select Cancel.
Check its the right contact and Membership.
Then, confirm the cancel.
That's it! Rinse and repeat.
Every time you cancel a membership you'll see the label update in the Status column.
All done. Top stuff!