You take your neatly coiled extension (photo 1) off the hook, toss it out and it ends up looking like photo 2 and takes 10 minutes to unkot the mess. Longer if you're in a rush! That's because you probably coiled it up something like in photo 3. What happens when you do it like this is that you have to twist the cord once every loop to make it lie flat. Nice and easy when winding up but mission impossible when uncoupling. Hence the tangle.
The next steps show two easy ways of avoiding it all
Step 1: Method 1
2. Bring the plug and socket ends together, forming a loop
3. Plug the plug into the socket. If it's a single face socket don't worry, plug it in anyway.
4 & 5. Pick up either the plug or the loop end and coil the double looped extension together (as if the two were one cord) EXACTLY as you would have done normally.
6. Toss it out. É vóila!
The math behind this is that by plugging the ends together and then coiling the loop up you create a twist in one direction in the one leg of the loop and a twist in the other direction in the other. These cancel each other when you toss it out.
If you are coiling a rope, go through the same steps but just tie a knot in the loose ends.
This method works fine for reasonably flexible cords. For some reason I haven't worked out, stiffer/thicker cords and hoses don't cooperate... Go figger
Method 2 follows below
Step 2: Method 2
1. Lay the starting end over your palm and wind the trailing end anticlockwise up, around and behind your thumb and then down, crossing it over the starting end to between the little and ring fingers.
2. Carry on, going clockwise around and behind the little finger, crossing the palm back up and anticlockwise around the thumb.
3 & 4. Keep going in this figure of eight pattern until you have about 1/2 a metre left
5. Slip the bundle off your hand and use the last half metre to tie the bundle up.
6. To uncoil, loosen the bundle and pull apart.
É vóila again
The math is that each successive half of the figure eight cancels the twist induced in the previous one.
Depending one the size of your hands you can coil up quite a long rope this way. I've managed up to 20 metres of the rope in the photos.