Don't know how long a board you're riding - obviously the longer the board, the harder it is to pivot.
Most of the beginner guides I read early on told me to "twiddle my legs like egg beaters to spin the board". Yes...that works, but just sitting there and twiddling your legs is an awfully slow way to turn.
So try it this way instead -
We'll assume you're sitting somewhere near the center of your board. When you want to turn, reach down and grab the rails close to your legs, and simultaneously push yourself back on the board and pull the board forward. You want to end up sitting pretty close to the tail, with the most of the board sticking up out of the water in front of you at a steep angle. Putting your weight all the way back by the tail will make it very easy to pivot the board. At this point you can leave your leading hand on the rail, and do a combination of twisting your hips, twirling your legs, and even pushing off against the water with your opposite hand to get the board spinning around.
It might take a while to get use to sitting so far back, as the board will be a lot less stable like this, but it won't take long. Of course wind is a major factor when you've got so much of the board sticking out of the water. More than once I've spun around only to get blown backwards as a strong offshore wind grabs most of my 9' board

This is a useful thing to practice between sets, or on flat days. Just sit there and spin
