>>Don't use plain wall in the studio to spot on. It's too hard to find again. Most studios don't have targets painted on the walls, but anything that you can see easily can work.
>Try to keep your head from moving as long as you possibly can before whipping it around. Don't anticipate your head move - delay, delay,delay
Agreed for piroettes. But for double tours I think it helps to initiate the head spot earlier. In fact I try to do it quite early. It is difficult to get around twice in the short time you are airborne and an early first spot healps a great deal.