Please note - for users on the latest iOS 7 version of our app:
As Foursquare continues to grow, we have decided to remove the ability to privately check in. If you don't wish to share your location, we'd encourage you to still use Foursquare to get out and explore awesome places nearby! All past private check-ins will remain private!
For all other platforms:
Feel like checking in to remember the day but don't feel like sharing it with everyone? To hide a check-in from your Foursquare friends but still have it show up (just to you) in your personal check-in history, tap the icon that looks like a group of friends so that is changes to a 'lock' on the side of the check-in screen before you hit 'check in.' Once you want to check in publicly again, tap the lock button until it looks like a group of friends.
Private check-ins will not be visible to the public or your foursquare friends. These check-ins do not assist in earning mayorships nor badges. To view these check-ins, simply navigate to your history page.
Note: private check-ins cannot be turned into public check-ins after the fact, nor vice versa.