Visit the Netflix home page and sign in. Go to the "Your Account" tab, which can be accessed via a drop-down menu to the right of the search bar in the upper right-hand corner of your home screen. Once on the "Your Account" page, you'll see a button that says "Cancel Membership" directly under "Membership and Billing," the first heading on the page. Click this button and follow the instructions to cancel your membership.
Even if you cancel your membership, you'll still be able to stream movies and television shows until your current billing period elapses. In addition, Netflix keeps your streaming account on file for a year after you have canceled your membership. This means you can cancel your membership for a couple of months and then go right back to it by renewing it and resuming payments, with all of your previous viewing history and preferences still available.