Crouch on the bike to compress up both tyres, then choose your rotation before take-off and initiate a slight turn before you jump.
Emphasize the rotation with your torso during your jump impulse and swing your hips to the opposite side.
Taking-off, re-align the bike with your torso and carry-on with the rotation by pulling further on the handlebars. Land backwards, don't use the brakes but back-pedal instead to stop progressively. Alternatively you can give a sharp swing in the bars to finish off the turn with an extra 180° of spin over the rear wheel.
180° bunny hop
The next step is to land sharp with your back wheel on top of an obstacle instead of clearing it. This variation of the bunny hop is usually performed at a lower speed, leaning further back during the extension to compensate for the blunt stop that will tilt the bike forward upon landing.