All tips that you write (and the photos you attach to them) will be viewable by the public. Please keep this mind whenever you choose to leave a tip!
Tips are public notes that you leave on a location for friends and other Foursquare users about experiences you recommend (or recommend be avoided) such as: "Get the off-menu butterscotch milkshake" or "Stay away during the morning coffee rush. You'll get better service after 11am!" Think of tips as a virtual version of something you would share with a friend to make their experience at a favorite place that much better.
To add a tip, go to a location page in the mobile app and scroll down. Tap the 'add a tip' button and write a little piece of wisdom (and upload a photo!) to leave behind for future visitors.
To edit a tip, find the tip you want to change on the place page and click the ‘Edit’ button. Note that you can only edit tips via the web and not the mobile app.
To delete a tip you've added via the mobile app, tap through to the tip detail, then scroll down and hit 'delete.' On the web, click the time/date on the tip, hover over the tip detail, and click the gray 'x' that appears.