(a) take a note of where people are meeting, the mobile phone number of the person you're meeting, and a mobile phone; or
(b) assume that because you regularly drink in this park, the people you're meeting will be in the 'obvious' place.
Sorry, everyone I was supposed to be meeting! I clearly had a brain transplant sometime early evening. I hung around the park for a while in the hopes of spotting someone I knew, and then went home. Am idiot.