It might sound quite obvious that to make the kayak turn, you just have to paddle harder on the opposite side. But actually that technique mostly just increases the overall speed and does very little to turn the kayak. We need to modify our forward paddling stroke a bit and do a so called forward sweep.
It is a good technique to be your primary steering stroke, because it doesn't slow you down and makes it easy maintain your paddling rhythm.
Forward sweep stroke can be done when the kayak is moving, or when it is standing still.
First take a regular forward paddling grip from the paddle. Place the blade into the water as forward as you can easily reach and keep the power face of the blade pointed away from the kayak. Keep the other hand fairly low.
Start doing a big arc that starts close to the bow and ends near the stern. Do the stroke by rotating your torso and try to keep your posture otherwise as still as possible.
At the beginning of the stroke, the kayak's bow is pushed away from the paddle, and at the end the stern is pulled closer to the paddle, making the kayak turn to the opposite side of the stroke.
Sometimes only a little change to the kayak's direction is needed, and then you can do a stroke that is something in between the sweep stroke and forward paddling stroke.
To make the kayak turn rapidly on its place, a good addition to forward sweep stroke is a reverse sweep stroke. It is just a forward sweep done backwards, starting from the back and ending close to your toes.