I have people follow me to my car at the grocery store when they notice I'm in a good spot (there are other, less desirable spots available, mind you). I take my sweet time loading my bags make sure nothing will tip over in transit. And during the time I'm loading, sometimes I decide I need something from the adjacent liquor store.
I've never understood why people sit and wait for spots when there's spots available. Drive around. If someone is pulling out, sure, but don't watch people load their shit up.