With room-temperature fish, get a pan really hot, add a little butter/oil and salt and put the fish in it. Sear it quickly on one side so it gets a little crust then immediately turn off the heat, leaving the fish in the pan.
I have to say it seems to work! The fish I cooked using this tip was probably the most "perfectly" cooked as I've ever been able to achieve so far. However, I made a slight tweak...I used a fish straight out of the refrigerator, turned off the heat almost as soon as I placed the fish in the frying pan, and then flipped it over after three minutes...Still seemed to do the trick.