When I first switched to Look clipless pedals in '93, I started using them just a couple of weeks before the Bicycle Ride Across Georgia. On the first day of BRAG, I fell over at the first traffic lights we came to in the first three towns along the route because I forgot to unclip before stopping. After that, one of my friends started riding behind and reminding me to unclip every time we approached a stop. He had a large time that evening telling everyone in camp how stupid I looked, so I drank his beer all night.
I have very rarely had a problem with unclipping since then.