Another descent one which factors in groundspeed...
Observe groundspeed, add a '0' then half it, this figure becomes your VS for the descent which is commenced at a distance from destination of 3x height:
eg. 23,000' at 400 kts G/S = A descent rate of 2000 fpm commenced at 69 nm from destination. Remember to adjust VS for any increase in G/S during descent, and factor in a few miles to slow down at the end.