I've found the '1 yd off for every 3 ft down' rule to be pretty good for 7 iron or longer shots. 8 iron - wedges have higher trajectory and come back to earth in more vertical flight path, reducing roll-out, thus I reduce the yardage correction a bit less for each increase in loft - so mid wedge (80 yd rated) I might use only 1 yd of reduction for every 4 ft of drop, and so forth.
You need to know whether you're hitting into an up-sloped, flat, or down-sloped green, and adjust spin and distance accordingly: less back- spin into up-sloped green and a bit more power, and more backspin with less power into down-sloped green.
All this assumes you've taken notes on carry distance and total distance after roll-out, for your equipment set (clubs & ball played)! You do have to land it on the green or fringe on the carry, generally.
Good luck