The Hanging method, finger method and the Leave-it-out-in-the-Sun method are all good ones that work well. In addition tho I have also found if you take a rag and spray it with Armor-All or other leather/vinyl/tire treatment fluid, while you coil it or run it
thru your fingers tightly before layting it out and let it sit, this can help with the new memory it will get. Another method whcich I know some houses will do is apply a VERY lite coating of Linseed Oil to the layed out cable or as its coiled. The Oil soaks into the rubber and warms up and helps the memory--but you should make sure its DRY and all wiped off before putting it away.
VERY VERY IMPORTANT NOTE about Linseed Oil--You need to apply it lightly, let it DRY and watch it for a few hours after applying, and keep it away from flammable items. Linseed Oil WILL make its own exothermic reaction and heat up to a flash point--the oil helps heat up the cable
jacket to give a good memory. BUT Linseed Oil is VERY VERY dangerous to use and work with if not taking precautions--fires have started from rags moist with Linseed Oil tossed into a garbage can. You MUST let it all evaporate and dry off before discarding rags wet with Linseed Oil--or soak them in water before tossing...else you can expect a fire to happen...
JMO...
-w